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APRAGMATICLEGALEXPERTSYSTEM
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Tomyparents,KevinandMarli,fortheirunfailingloveandsupport;
andtoPaula: forwhom,butforwhom. . .
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APragmaticLegalExpertSystem
jamespopple
VisitingFellowTheAustralianNationalUniversity
DartmouthAldershot BrookfieldUSA Singapore Sydney
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James Popple 1996
All rights reserved. No part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by any means, electronic, mechani-cal, photocopying, recording, or otherwise without the prior permission of DartmouthPublishing Company Limited.
Published byDartmouth Publishing Company LimitedGower HouseCroft RoadAldershotHants GU11 3HREngland
Dartmouth Publishing CompanyOld Post RoadBrookfieldVermont 05036USA
British Library Cataloguing in Publication DataPopple, James
A pragmatic legal expert system. - (Applied legalphilosophy)1. Law 2. Expert systems (Computer science)I. Title340'.0285'533
Library of Congress Cataloging-in-Publication DataPopple, James, 1964-
A pragmatic legal expert system / James Popple.p. cm. (Applied legal philosophy)
Includes bibliographical references and index.ISBN 1-85521-739-21. SHYSTER. 2. LawMethodologyData processing. 3. Law-
-Interpretation and constructionData processing. 4. Expertsystems (Computer science)Australia. 5. LawAustralia--MethodologyData processing. I. Title. II. Series.
K212.P664 1996340'.1dc20 96-7058
CIP
ISBN 1 85521 739 2
Printed in Great Britain by the Ipswich Book Company, Suffolk
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ContentsFigures ixSeriespreface xiPreface xiiiChapter1: Legalexpertsystems 11.1 Introduction 21.2 Jurisprudence 51.3 Jurimetricsandthebehaviourists 191.4 Rule-basedsystems 241.5 Case-basedsystems 381.6 Hybridsystems 441.7 Conceptualmodels: deepandshallow 461.8 Conclusion 49
Notes 50Chapter2: Apragmaticapproachtocase law 612.1 Introduction 622.2 Designcriteria 622.3 Amodeloflegalreasoning 662.4 Experts,users,andexpertusers 692.5 Knowledgerepresentation 702.6 Aspecificationlanguage 742.7 Weightingattributes 752.8 Detectingattributedependence 792.9 Calculatingdistances 812.10 Nearestcasesandnearestresults 892.11 Writingareport 922.12 Safeguards 1012.13 Testingandevaluation 1032.14 Conclusion 111
Notes 118v
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vi Apragmatic legalexpertsystem
Chapter3: ImplementingSHYSTER 1253.1 Introduction 1263.2 TheShystermodule 1283.3 TheStatutesmodule 1283.4 TheCasesmodule 1303.5 TheTokenizermodule 1313.6 TheParsermodule 1323.7 TheDumpermodule 1383.8 TheCheckermodule 1413.9 TheScales module 1463.10 TheAdjuster module 1473.11 TheConsultantmodule 1473.12 TheOdometermodule 1483.13 TheReporter module 1513.14 Conclusion 159
Notes 159Chapter4: Casestudies 1634.1 Introduction 1644.2 AsimulationofFINDER 1644.3 Theauthorizationofcopyrightinfringement 1734.4 Employeesandindependentcontractors 1914.5 The implicationofnaturaljustice 2074.6 Conclusion 230
Notes 234Chapter5: Conclusion 2435.1 Introduction 2445.2 EvaluatingSHYSTER 2445.3 Futureresearch 2505.4 ThecontributionoftheSHYSTERproject 252
Notes 253
AppendixA: Examplereports 255A.1 Introduction 256
Notes 256A.2 ReportfileforParkerv.BA 257A.3 ReportfileforAPRA v.Jain 263A.4 ReportfileforRePorter 270A.5 ReportfilesforAinsworthv.CJC 278
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Contents vii
AppendixB: Acompleteexample 289B.1 Introduction 290
Notes 290B.2 LogfileforBWIU v.Odco 291B.3 DumpfilefortheEmployee specification 294B.4 ProbabilitiesfilefortheEmployee specification 322B.5 WeightsfilefortheEmployee specification 323B.6 DistancesfileforBWIU v.Odco 323B.7 ReportfileforBWIU v. Odco 331
Bibliography 341Cases 367Statutes 373Index 375
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Figures2.1 Structureofanexamplespecification 712.2 Formsoffunctionaldependence 812.3 Two-wayassociationtable 852.4 Exampledistances 912.5 SHYSTERsalgorithmforchoosingcases 942.6 SHYSTERsalgorithmforusingcases: partA 962.7 SHYSTERsalgorithmforusingcases: partB 972.8 SHYSTERsalgorithmforusingcases: partC 983.1 SHYSTERscommandlineswitches 1293.2 KeywordsinSHYSTERsspecificationlanguage 1313.3 EBNFdefinitionofSHYSTERsspecificationlanguage 1333.4 AttributevaluesfortheEmployeearea 1393.5 Exampleattributevalues 1423.6 Probabilitiesforexampleattributes 1433.7 ExtractfromprobabilitiesfortheEmployeearea 1463.8
Similarity
measures
149
3.9 DistancesforBWIU v.Odco 1503.10 ExtractfromthelogfileforBWIU v.Odco 1574.1 ProbabilitiesfortheFinderarea 1704.2 WeightsfortheFinderarea 1714.3 DistancesforParkerv. BA 1744.4 ProbabilitiesfortheAuthorizationarea 1804.5 WeightsfortheAuthorizationarea 1814.6 DistancesforCBS v. Ames 1844.7 DistancesforNarichv. CPT 1984.8 Relationshipbetweenareas intheNaturalspecification 2104.9 WeightsfortheNaturalspecification 2154.10 ProbabilitiesfortheNatural specification 2164.11 DistancesforTwistv.Randwick intheNaturalarea 2194.12 Summaryoftestcases 2314.13 Summaryofgeneratedtesting 233
ix
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SeriesprefaceThe objective of the Dartmouth Series in Applied Legal Philosophy is to publish work which adopts a theoretical approach tothestudyofparticularareasoraspectsoflawordealswithgeneraltheoriesoflawinawaywhichfocusesonissuesofpracticalmoralandpoliticalconcerninspecificlegalcontexts.
Inrecentyearstherehasbeenanencouragingtendencyforlegalphilosophers to utilize detailed knowledge of the substance andpracticalities of law and a noteworthy development in the theoretical sophistication of much legal research. The series seeks toencouragethesetrendsandtomakeavailablestudiesinlawwhicharebothgenuinelyphilosophicalinapproachandatthesametimebasedonappropriatelegalknowledgeanddirectedtowardsissuesinthecriticismandreformofactuallawsandlegalsystems.
The series will include studies of all the main areas of law,presented ina mannerwhichrelates totheconcerns ofspecialistlegal academics and practitioners. Each book makes an originalcontribution to an area of legal study while being comprehensibletothoseengaged inawidevarietyofdisciplines. Their legalcontent is principally Anglo-American, but a wide-ranging comparative approach is encouraged and authors are drawn from avarietyofjurisdictions.
TomD.CampbellSeries
Editor
FacultyofLaw
TheAustralianNationalUniversity
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PrefaceThe history of the development of legal expert systems has, forthemostpart,beencharacterizedbythedevelopmentandimplementationofcomplexmodelsoflegalreasoning.
This book aims to show that a legal expert system need notbe based upon a complex model of legal reasoning in order toproduceusefuladvice. Itadvocatesapragmaticapproachtothedesignof legalexpertsystemsanapproachbasedontheway inwhich lawyersdealwiththelawonaday-to-daybasis.
It argues that a system based upon a simple model of legalreasoningcanstillproducegoodadvice,wherethatadviceisevaluatedbyreferencetotheaccuracyofthesystemspredictionsandtothequalityofitsarguments. Furthermore,suchasystem,withitssimplerknowledgerepresentationstructure,makessimplertheprocessofknowledgeacquisition.
Theseargumentsaremadetheoretically,andthenbyexample.Ihavedevelopeda legalexpertsystemwhich isbasedonapragmaticapproachtothe law. Thedevelopmentandtestingofthatsystem,calledSHYSTER,isdescribedinthisbook.
SHYSTERisofageneraldesign,sothatitcanoperateindifferentlegaldomains. Itwasdesignedtoprovideadvice inareasofcaselaw that have been specified by a legal expert using a speciallydevelopedspecification language.
SHYSTER isacase-based legalexpertsystem. Itsknowledgeofthe law isacquired,andrepresented,as informationaboutcases.Itproduces itsadvicebyexamining,andarguingabout,thesimilarities and differences between cases. By contrast, a rule-basedexpert system represents the law using rules. A hybrid systemuses both rule-based and case-based techniques. SHYSTER hasbeendesignedsothatitcanbelinkedwitharule-basedsystemtoformahybridlegalexpertsystem.
xiii
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xiv Apragmatic legalexpertsystem
AlthoughSHYSTERattemptstomodelthewayinwhichlawyersarguewithcases, itdoesnotattempttomodeltheway inwhichlawyers decide which cases to use in those arguments. It usesstatisticaltechniquestoquantifythesimilaritybetweencases,andchooses cases on the basis of thatsimilarity measure. ItsrepresentationstructurewasdesignedtobeassimpleaspossiblewhilecomplexenoughtoallowSHYSTER toproducegoodadvice.Thebodyofthisbookisdividedintofivechapters:
Chapter1discussespreviousworkofrelevance tothedevelopment of legal expert systems. The value ofjurisprudencetothedevelopmentofsuchsystemsisalsodiscussed,andtheadoptionofapragmaticapproach(asopposedtoajurisprudentiallypureapproach)isrecommended.
A pragmatic approach is proposed in chapter 2. It incorporatesasimplemodelof legalreasoning,andusesasimpleknowledge representation structure. Comparisons are madebetween
this
approach
and
others.
This
approach
is
adopted
forthedevelopmentofSHYSTER. Specificdesigncriteria forSHYSTERaredetailed,andmethodsoftestingandevaluatingthesystemarediscussed.
The implementation of SHYSTER is explained in chapter 3.The twelve modules that comprise SHYSTER are described,andtheiroperationisdemonstratedusingexamples.
FourdifferentspecificationshavebeenwrittenforSHYSTER,and these are used as the basis of case studies in chapter 4.Eachspecificationrepresentsadifferentareaofcaselaw. Several different methods are employed to test SHYSTER andthesespecifications.
Inchapter 5, conclusions are drawnabout SHYSTER and itsapproach to case law. Some enhancements to SHYSTER aresuggested, avenues of future research are identified, and thenature of the contribution made by the SHYSTER project isdiscussed.
There are two appendices to this book. Appendix A providesexamplereportsrelatingtoeachofthefourspecifications. EachofthesereportsisSHYSTERsadviceononeofthetestcasesusedinchapter4. AcompleteexampleofSHYSTERsoutputforanothertestcaseisgiveninappendixB.
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Preface xv
IhaveendeavouredtoexplainSHYSTER anditsapproachtocaselawasclearlyaspossible. Occasionallyespecially in chapters 2and3thisexplanationinvolvesrecoursetomathematicaldetail.Readers for whom the sight of a formula provokes either greatfearorprofoundindifference,andwhodontfeelaneedtounderstandtheintricaciesofSHYSTERsinnerworkings,areadvisedtodisregardanyoffendingmathematics.Forthosewhowouldliketoexperimentwiththesystem,SHYSTERandthecaselawspecificationsdiscussedinthisbookareavailableontheworldwidewebathttp://cs.anu.edu.au/software/shyster.ThisbookisbaseduponmydoctoralthesiswhichIwrotewhilearesearchstudentatTheAustralianNationalUniversity,andcompleted in April 1993. I thank the members of my supervisorypanelRobinStanton,RogerClarke,PeterDrahosandMalcolmNeweyfor theircounseland encouragement, andRobinCreykeandPhillipaWeeksforgivingsofreelyoftheirtimeandlegalexpertise. I have also been provided with valuable advice on thisworkbymythesisexaminersKevinAshley,BobMolesandAlanTyreeandbyRichardSusskind.
Notwithstandingthisassistance, forwhich Iammostgrateful,responsibilityforthisbookremainsmine.
JamesPoppleApril1995
http://cs.anu.edu.au/software/shyster/http://cs.anu.edu.au/software/shyster/ -
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shy.ster \ shst (r)\ n -s [prob. after Scheusterfl1840 Am. attorney frequently rebuked in a New York court for pettifoggery] : one who is professionallyunscrupulousesp. inthepracticeof laworpolitics. . .
WebstersThirdNewInternationalDictionary (1961)shyster( a st (r)). . . [Ofobscureorigin.
Itmightbe f.shya.(sense7,disreputable)+-ster;butthissenseoftheadj. isapp.notcurrentintheU.S.]
. . . Alawyerwhopractisesinanunprofessionalortrickymanner;especially,onewhohauntstheprisonsandlowercourtstopreyonpettycriminals;hence,any one who conducts his business in a tricky manner (Funks Stand. Dict.1895). Alsoattrib.oradj. Orig.andchieflyU.S.slang . . .
TheOxfordEnglishDictionary (secondedition,1989)shyster. An unscrupulous lawyer (note that the definition presumes theexistenceofscrupulousones) . . .
The term does not come fromas suggested in various dictionariesthesurnameScheuster,supposedlyalawyernotedforshyster-likepractices;fromthe name of the Shakespearean character, Shylock; . . . or from any of thevariousmeaningsofshy(e.g.,tobeshyofmoney). Rather. . . shyster evolvedfrom the underworld use ofshiser, a worthless fellow, which derived in turnfrom the German scheisse, excrement, via scheisser, an incompetent person(specifically,onewhocannotcontrolhisbodilyfunctions). . .
HughRawson(1991)ADictionaryofInvective
xvii
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1 LegalexpertsystemsIntheyahooworldofcomputerpublicrelations,itisoftentheloudestmouthswhichleadtheunsuspectingcomputeruser intothat lonelycanyonofemptypockets and broken promises. It now seems . . . that parts of the academicworldarefastapproachingthatdecibellevelsofarachievedonlybycomputersalesmen. Thus. . . itseemsthatspacecanonlybebookedontheband-wagonifone ispreparedtomakemoreoutrageousclaimsthanthenextman. AndsuchclaimsarebeingmadefortheapplicationofAItothe law.
PhilipLeith(1986)1
Thecomputerscientists,encouragedbythemodernpositivists,failtorecognize. . . thatlaw,positivemoralityandethicsareinseparablyconnectedpartsof a vast organic whole. Judgments are involved at every stage of the legalprocessandmachinescannotmakejudgments. Instatingthatlegalrulescanbe applied without furtherjudgment; that they apply in an all or nothingfashion; that legal decision making follows the form of the syllogism or thatit is a pattern-matching routine, the modern positivists,joined now by thecomputerscientiststakeusalongadangerousroad.
RobertN.Moles(1987)DefinitionandRule inLegalTheory:
AReassessmentofH.L.A.Hartand thePositivistTradition2
Aussi, lorsquun homme se rend Thus when a man takes on absoluteplus absolu, songe-t-il dabord a power,hefirstthinksofsimplifyingthesimplifier les lois. On commence, law. In such a state one begins to be
dans cet Etat, a etre plus frappe moreaffectedbytechnicalitiesthanbydes inconvenients particuliers, que thefreedomofthepeople,aboutwhichde la liberte des sujets dont on ne oneno longercaresatall.sesouciepointdutout.
Montesquieu(1748)De lEspritdes lois3
1
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2 Apragmatic legalexpertsystem 1.1
1.1 IntroductionThis chapter reviews previous work of relevance to the designof legal expert systems. Jurisprudence and its value to the development of such systems is discussed (1.2) and the field ofjurimetricsandsomebehaviouristicresearchisexamined(1.3).Thedevelopmentoflegalexpertsystemsisdiscussedunderthreeheadings: rule-based,case-based,andhybridsystems.4
Rule-based systems are examined first (1.4), and special attention is paid to the work of four projects. The problems ofknowledgeacquisitionandrepresentation,andfactrepresentationare also discussed (1.4.5 and 1.4.6). Rule-based systems havebeenusedtorepresentstatutesandcases. However,asexplainedin1.4.7,rule-basedsystemsarefundamentallyinadequateforrepresentingcaselaw.
Case-based systems areexamined(1.5)andthreeprojectsareoutlined. Systemsthatuserulesinordertorepresentcaselawareconsidered to be rule-based systems; only systems which adoptcase-based reasoning methods are considered to be case-based.Applying this distinction is usually straightforward, though notalways.5 Attempts have been made to use semantic networks torepresentcaselawbut,asexplainedin1.5.4,theyarenotsuitedtothetask.
Hybrid systems (1.6) employ both rule-based and case-basedmethods.
Thesearchforconceptualmodels oflegalreasoningisdiscussed(1.7). Finally,conclusionsaredrawnfromtheliteratureastothebestapproachtothedesignoflegalexpertsystems(1.8).Butfirstitisnecessarytoexplainwhatismeantbyalegalexpertsystem,andtooutlinesomekeyconcepts.1.1.1 LegalexpertsystemsTherangeofcomputerapplicationsinthelawiswide. Itextendsfrom general applications, of use to lawyers, to applications designed specifically for the law. This book isconcerned onlywitha subset of those systems that make use of artificial intelligence(AI)techniquestosolvelegalproblems.
Legal AI systems can usefully be divided into two categories:legalretrievalsystemsandlegalanalysissystems.6 Legalretrieval
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3 1.1 Legalexpertsystems
systems allowlawyerstosearchthroughdatabasescontainingdetailsofstatutesanddecidedcases. AItechniquesmaybeemployedto simplify this task: e.g. by searching for keywords which havenotbeeninputbytheuserbutarededucedtobeequivalentto,orsufficientlyrelatedto,theinputkeywords.7 Legalanalysissystemstake informationaboutasetoffactsanddeterminetheramificationsofthosefactsinagivenareaoflaw.
Mehl claims that there is no fundamental difference betweenthese two categoriesthat the difference is one of degree only.8ShannonandGolshanisuggestthatthedifferencebetweensystemsbasedonaconceptualmodeloflegalanalysisandtextretrievalsystems is that the latter do not understand any area of thelaw.9 Similarly, Susskind says that knowledge-based systems,as opposedto databasesystemsare capable of applyingtheirknowledgeofthelawtotheproblemdatapresentedtothem.10
A better distinctionone which avoids the vexed question ofwhetheranyAI systemcanreallybesaidtoknoworunderstandanythingcanbemadebyreferencetotheoutputofthesystem.The
output
from
alegal
analysis
system
is
such
that,
if
it
had
been
produced by a human, that human would be said to have legalexpertise. By contrast, the output from a legal retrieval systemcould be produced by a human possessed of no legal expertise;suchoutputisusedin,andisnottheproductof,legalanalysis.11
Thisbookisconcernedonlywithlegalanalysissystems.Legal analysis systems can be divided into two categories: judgmentmachinesand legalexpertsystems.
Ajudgmentmachine isamachinedesignedtoreplaceahumanjudge. Suchmachineswerefirstproposedfortyyearsago,thoughnosuchproposalshavebeenmade fornearlytwodecades. Writingsonjudgmentmachinesarediscussedbelowbecausetheyareofhistoricalinterest,andbecausetheideaofajudgmentmachineraisessome issues which arealso relevant to the secondcategoryoflegalanalysissystems: legalexpertsystems.
A legal expert system, as the term is used in this book, is asystemcapableofperformingata levelexpected ofa lawyer. AIsystemswhichmerelyassistalawyerincomingtolegalconclusionsor preparing legal argument are not here considered to be legalexpert systems; a legal expert system must exhibit some legalexpertiseitself. Thisdefinitiondoesnotexcludesystemsthatcanonly be used by legal experts; several systemsincluding SHYSTERhavebeendevelopedforuseexclusivelybylawyers.12
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4 Apragmatic legalexpertsystem 1.1
1.1.2 SourcesoflawThe
law
in
so-called
common
law
countriese.g.
Australia,
Britain, Canada and the USAis derived from legislation and from
caselaw.Legislation, or statute law, consists of statutes and delegated
legislation. InAustralia,statutesaremadebytheFederalParliament,oraStateParliament,andenactedwhengivenroyalassentby the Governor-General, or a State Governor. Delegated legislation(rules,regulations,ordinances,by-laws,etc.) ismadebyapersonorbodytowhom legislativepowerhasbeendelegatedbystatute.
Caselaw,orthecommonlaw,isjudge-madelaw:judicialresolutionsofspecificdisputes. Thesourcesofcaselawarethepublishedreportsofthecasesasheardbeforevariouscourts.
Legislation takes precedence over case law;13 parliaments canoverridejudge-madelawbylegislativeenactment. However,judgeshavethetaskofdeterminingthemeaningoflegislation.
Any legal expert system which seeks todeal with the law in acommon lawcountrymustaccount forbothstatute lawandcaselaw.1.1.3 ThedoctrineofprecedentThedevelopmentofcase law isbasedupontheprincipleofstaredecisis whichholdsthatcourtsshouldapplythedoctrineofprecedent. Morrisetal.summarizethegeneralrulesofthedoctrineofprecedentasfollows:
eachcourtisboundbydecisionsofcourtshigherinitshierarchy; adecisionofacourt inadifferenthierarchymaybeofconsid
erableweight,butwillnotbebinding; onlytheratiodecidendi ofacaseisbinding; anyrelevantdecisions,althoughnotbinding,maybeconsidered
andfollowed;andprecedentsarenotnecessarilyabrogatedbylapseoftime.14
Courtshave a tendencyto follow similar cases, even when notstrictlyboundtodoso. AccordingtoCross:
It is a basic principle of the administration ofjustice that likecases should be decided alike. This is enough to account for thefact that, in almost everyjurisdiction, ajudge tends to decide a
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1.2 Legalexpertsystems 5
case in the same way as that in which a similar case has beendecidedbyanotherjudge.15Thereisconsiderableargumentabouttheextenttowhichjudges
actually apply the doctrine of precedent.16 Some legal theoristscontend that the doctrine is simply part of the public discoursethatjudgesusetojustifytheir decisions. Stoneclaims thatthedegreeofcertaintyandstabilityinthelawsecuredbythedoctrineofstare decisis is far lessthan itappearstobe,andthatoneoftheimportantsocialfunctionsofthedoctrineistomaintainatamaximumthefeelingandappearanceofcertaintyandstability.17Yet,judgesofthehighestcourt inAustraliahavebeenknowntofollowpreviouscaseswhichtheybelievedtobewronglydecided.18
What is clear is thatjudges use previously decided cases tojustify their decisionsif not to reach themand that lawyersusepreviouslydecidedcases in legalargument. Any legalexpertsystem which deals with case law assumes theapplication of thedoctrineofprecedent,atleasttothisextent.1.1.4 TerminologyFor consistency, the following three terms are used in this bookforavarietyoftermsthatareusedthroughouttheliterature. Anattribute is a legally important fact; some authors use thewordsdescriptor,dimension,factor,featureorvariable. Theinstantcase isthesituationaboutwhichtheexpertsystem is interrogated;thisissometimescalledtheactualcase,thecurrentfactsituation,thehypotheticalcaseorthenewcase. Leading cases make up the case base of a legal expert system; somecallthesethereferencesetorthetrainingset.1.2 Jurisprudence1.2.1 TheimportanceofjurisprudenceFor centuries, lawyers and philosophers have written on, and arguedabout,thenatureofhumanlaws. Onthefaceofit,itwouldseemsensibleforthedeveloperofalegalexpertsystemtohaveregardtothisjurisprudentialtheorybeforedesigningher/hissystem.However, asSusskindcomplained in 1987, most of thepublishedresearchonvariouslegalexpertsystemsmakesnouseofjurisprudentialresources.19
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6 Apragmatic legalexpertsystem 1.2
Some expert system researchers have been doubtful as to thevalue ofjurisprudence to their research. Niblett, for example,claimsthatasuccessfulexpertsystemislikelytocontributemoretojurisprudencethantheotherwayround.20 Susskinddisagrees:
It is beyond argument . . . that all expert systems must conformto somejurisprudential theory because all expert systems in lawnecessarily make assumptions about the nature of law and legalreasoning. To be more specific, all expert systems must embodytheories of legal knowledge, legal science, the structure of rules,the individuation of laws, legal systems and sub-systems, legalreasoning, and of logic and the law (as well perhaps as elementsof a semantic theory, a sociology, and a psychology of law), theories that must all themselves rest on more basic philosophicalfoundations. Ifthis isso, itwouldseemprudentthatthegeneraltheoryoflawimplicitinexpertsystemsshouldbeexplicitlyarticulated using (where appropriate) the relevant works of seasonedtheoreticians of law. Perhaps the reason that there is, as yet,no overwhelmingly successful system is that the vast corpus ofappositejurisprudential material has not yet been tapped in theconstructionprocess.21Althoughitistruethatalllegalexpertsystemsnecessarilymake
assumptionsaboutthenatureof lawand legalreasoning, itdoesnotfollowthattheymustconformtosomejurisprudentialtheory.A lawyer must have a model of the law (maybe unarticulated)which includes assumptions about the nature of law and legalreasoning, but that model need not rest on basic philosophicalfoundations. It may be a pragmatic model, developed throughexperience within the legal system. Many lawyers perform theirworkwithlittleornojurisprudentialknowledge,22 andthereisnoevidence to suggest that they are worse, or better, at theirjobsthanlawyerswell-versed injurisprudence.
Susskind concedes that it is possible to build a legal expertsystemwithoutjurisprudentialinsight,butsuggeststhatsuchasystemwouldbeofverypoorquality:
Because successful legal knowledge engineering presupposes soprofound a familiarity with the nature of law and legal reasoning,itisscarcelyimaginablethatsuchamasterycouldbegainedotherthanthrough immersioninjurisprudence.23
Harris,himselfajurisprudent,takesadifferentview:People acquire those technical skills of legal reasoning and legalargumentation which make up the concept of good lawyer by
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7 1.2 Legalexpertsystems
immersingthemselvesinsubstantivelegalsubjects. Jurisprudencehastodo,notwiththelawyersroleasatechnician,butwithanyneed
he
may
feel
to
give
a
good
account
of
his
lifes
workeither
tofellowcitizens,ortohimself,ortoanygodstherebe.24
IfHarrisisrightandtheexistenceofgood(thoughjurisprudentially illiterate) lawyerssuggeststhathe isthenthe importanceofjurisprudenceto legalexpertsystemdesign isquestionable. Alegal expert system need only operate at the same level of abstraction as does a lawyer, rather than at the philosophical levelofajurisprudent. Thefactthatmany lawyershavemasteredtheprocessoflegalreasoning,withouthavingbeenimmersedinjurisprudence,suggeststhatitmayindeedbepossibletodeveloplegalexpertsystemsofgoodqualitywithoutjurisprudentialinsight.
Thisdoesnotmeanthat legalexpertsystemsdesignersshouldcompletely ignorejurisprudential literature. However, as a legalexpert system need not conform to anyjurisprudential theory, apragmaticapproachtoexpertsystemdesignmaybepreferabletoa
jurisprudentiallypureone. Susskind,asNiblettcomplains,givesthe role ofjurisprudence in the design of legal expert systems agreatersignificancethanitdeserves.25
Itiswellbeyondthescopeofthisbooktocoverthevastcorpusof appositejurisprudential material,26 however several areas of
jurisprudence of relevance to expert system design are discussedbelow.1.2.2 ScientificandmechanicaljurisprudenceThedictionarydefinesjurisprudence as:
Thesciencewhichtreats ofhuman laws (written and unwritten)ingeneral;thephilosophyoflaw.27
Poundreferstothescientificcharacterofthelaw:SirFrederickPollockgivesustheclewwhenhedefinesthereasonsthat compel law to take on this scientific character asthree: thedemandforfulljustice,thatisforsolutionsthatgototherootofcontroversies; the demand for equaljustice, that is a like adjustment of like relations under like conditions; and the demand forexactjustice,thatisforajusticewhoseoperations,withinreasonablelimits,maybepredictedinadvanceofaction. Inotherwords,themarksofascientificlaware,conformitytoreason,uniformity,andcertainty.28
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8 Apragmatic legalexpertsystem 1.2
Thisapproachtothelawhasbeenmuchcriticized. Frankcontendsthatuncertaintyisinherentinthelegalprocess,andthatseekingcertaintyingenerallegalprinciplesissimplyanexpressionofinfantileemotionalattitudeswhichhavepersistedintoadulthood.29
In his 1908 paper, Mechanical Jurisprudence, Pound distinguishesscientificjurisprudencefrommechanicaljurisprudence:
Romanlawinitsdecadencefurnishesastrikingexample[ofmechanicaljurisprudence]. TheValentinianlawofcitationsmadeaselection ofjurisconsults of the past and allowed their writingsonly to be cited. It declared them, with the exception of Papinian,equalinauthority. Itconfinedthejudge,whenquestionsoflawwereinissue,tothepurelymechanicaltaskofcountingandofdeterminingthenumericalpreponderanceofauthority. Principleswere no longer resorted to in order to make rules fit cases. Theruleswereathandinafixedandfinalform,andcasesweretobefittedtotherules.30
By
contrast,
Pound
says,
scientific
law
is
a
reasoned
body
of
principlesfortheadministrationofjustice.31Loevinger also argues that there is a role for science in law,
but sees little science injurisprudence. In 1949 he proposed analternativetojurisprudencewhichhetermedjurimetrics:
Thenextstepforwardinthelongpathofmansprogressmustbefromjurisprudence(whichismerespeculationaboutlaw)tojurimetricswhichisthescientificinvestigationoflegalproblems. . . Theinescapablefactisthatjurisprudencebearsthesamerelationtoamodernscienceofjurimetricsasastrologydoestoastronomy,alchemy to chemistry, or phrenology to psychology. It is basedupon speculation, supposition and superstition; it is concernedwith meaningless questions; and, after more than two thousandyears,jurisprudence has not yet offered a useful answer to anyquestionoraworkabletechniqueforattackinganyproblem.32
Thisproposalspawnedanewfieldofstudy,someworkfromwhichisdiscussedbelow.33
Loevingercallsthosewhofearthedangersofmechanizedjurisprudencequixoticanduncomprehending34thoughhewasnotamechanicaljurisprudenthimself.35 Some,however, sawthedevelopmentofcomputersasanopportunitytodevelopajudgmentmachine: amachinethatcouldreplaceajudge.
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9 1.2 Legalexpertsystems
1.2.3 JudgmentmachinesIn1955,Lasswellpredictedthat:
When machines are more perfect [sic] a bench ofjudicial robots. . . can be constructed. The machine would apply a system ofweightstoallegationsoffactmadebypartiestoacontroversy,andalsotothejustificationsadvancedinsupportoftheclaimsputforwardbyparticipants. Litigationcanproceedbycounselfortheplaintiff and the defendant pressing buttons that translate theircasesintothephysicalsignsbuiltintothemachine. Manyresultswouldbenodecision. However,themachinecouldbedesignedtosettleacontroversyofthiskindwitharandomoperation(bylot).36
Hewasnotaltogetherserious:Itisachallengingtaskforlegalhistorianstoassistinconstructingarobotwhoseweightswouldgivesubstantiallythesameresultasthoseproducedbythe[USSupreme]Courtatvariousperiods. Thetask would not be too difficult for somejustices on some issues.Butarobotfacsimileofthe lessrepetitivemembersoftheCourtwouldprovideagenuinechallengetotheengineers.37However,somehavetakentheideaofajudgmentmachinevery
seriously indeed. In 1949, Frank wrote that a logic machinemight disclose all possible available alternative legal rules, although judges would still have to exercise the the sovereignprerogativeofchoicebetweentherulesonthebasisofthejudgesconscious or unconscious notions of policy.38 Similarly Mehlwrote, in 1959, that a machine could perform some of the functionsofajudge,butthataroleforhumanswouldremainbecausethesolutiontoa legalproblemmaydependuponextra-rationalfactors, involvingthewholeofhumanexperience.39
Asrecentlyas1977,ithasbeenseriouslysuggestedthatajudgment machine could replace a humanjudge. DAmato proposedthatamachinecouldtaketherelevantfactsofacaseasinputandproduceanumber intherange1to+1(whereapositivenumberindicatesavictoryfortheplaintiff). Giventhemultiplicityoffactors,heclaims,aresultofzerowouldbeextremelyunlikely,40although it isnotclearwhythiswouldbeso. These factswouldbe determined by ajury, but the law would be decided by themachine. Somewhatgrudgingly,heallows foravestigeofhuman
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control: anappealcourtcouldreviewallofthemachinesdeterminations in a certain numerical range (e.g. 0.05 to 0.05) withinwhichthecaseswouldbesoclosethatare-examinationmightberequired. The review courts subsequent decision would then beincorporatedintothesystem.41
Theideaofhumanjudgesbeingreplacedbymachineshasbeentrenchantlycriticized. AccordingtoWeizenbaum:
The very asking of the question, What does ajudge . . . knowthatwecannottellacomputer? isamonstrousobscenity. Thatithastobeputintoprintatall,evenforthepurposeofexposingitsmorbidity,isasignofthemadnessofourtimes.
Computerscanmakejudicialdecisions. . . Theycanflipcoinsinmuchmoresophisticatedwaysthancanthemostpatienthumanbeing. Thepointisthattheyought notbegivensuchtasks. Theymayevenbeabletoarriveatcorrectdecisionsinsomecasesbut always and necessarily on bases no human being should bewillingtoaccept.42
ButDAmatoseesadvantages inreplacinghumanjudgesbymachines:Would we lose ajudges judgment, and how important wouldsuchalossbetoourlegalsystem? Surelycomputersdonotmakejudgments the way humans do, and so we would lose the humanaspectoflegaljudgments. Butwhatspecificallydowelosewhen we lose the humanness ofjudgments? Is humanjudgment
justaeuphemismforarbitrariness,discretion,orbias?43Bycontrast,Stonestressestheimportanceoflegalchangespringing from deviance, tentativeness, and even indecision injudgment.
It is these phenomena above all which promote ajudges sensitivitytonewideasortonewlyperceivedsocialsituationsandstirHamlet-like introspection. On these there rest some of the mainfoundations
of
the
social
good
we
call
justice.
44
Proponentsoftheideaofautomatedjudgesclaimthatsuchsystemswouldreducethecostofthelegalsystem,findinconsistenciesinthe law,andprovidea levelofcertainty inthe lawwhichdoesnotexistatpresent.45 DAmatoclaimsthatajudgmentmachinewouldallowpeopletoliveundertheruleoflawandnotundertheruleofpersons.46
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DAmatosargumentisbasedupontwoboldinitialpremises.Heassumesthat,fromajurisprudentialpointofview,thelawhasbeen made completely determinable. He also assumes that, if acomputer can beprogrammedto makejudicial decisions, humandiscretionwillhavebeencompletelyremoved.47
Hisviewsonjudgmentmachinesareextreme,andhavenotbeenwidely accepted. For the most part, designers of legal analysissystemshavefocusedonbuildingsystemswhichprovideadvicetolawyersortolaypeople,ratherthansystemswhichusurptheroleofjudges. However,manyofthesedesignershavemadeDAmatosfirstassumptionthatthelawiscompletelydeterminableoftentacitly.481.2.4 PetrifactionofthelawTheideaofajudgmentmachineremovinguncertaintyandambiguityinthelawraisesthepossibilityofthepetrifactionofthelaw.Thispossibility isalsorelevanttolegalexpertsystemdesign.
DAmatoclaims
that,
once
programmed,
the
law
would
become
settled. The computer would stop progress, although the legislature could always step in if anomalous results were beingproduced.49 Similarly, Kayton believes that the use of propositional logic could identify legalambiguity andprovideguidelinesforitsresolution. Heasks:
Wouldnoteachconcretedemonstrationofambiguityanditsresolution tend to rigidify the law and eventually destroy the veryflexibilitywhichhasmadethecommonlawviable? . . . Despitethedangers of generalization, it is submitted that . . . [this question]shouldbeanswered inthenegative. Informationbroughttobearinarationalpursuitisalwaysbetterthanignoranceorconfusion.Theeliminationofambiguities,ratherthanossifythelaw,wouldproduceanoptimumconditionforthepurposeful,intelligent,andefficientdevelopmentofthelaw.50
Schubert,anotherearlyresearcherinthisfield,isnotconvincedofthepossibility,ortheimportance,ofcertaintyinlaw. Hewrites:
. . . theidealofcertainty inlawistolerableonly inthecontextofanempiricalworldinwhichforcesinducingchangearesomanifoldthattheattainmentofthegoalisneverpossible.51Tyreearguesthatadeterministiccomputerjudgecouldover
rule himself if cases are added as they are decided.52 But as
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Poundpointedoutalmostninetyyearsago, theproblem ismorethanmereossificationofthelaw:
The effect of all system is apt to be petrifaction of the subjectsystematized. Perfectionofscientificsystemandexpositiontendstocutoff individual initiative inthe future,tostifle independentconsiderationofnewproblemsandofnewphasesofoldproblems,andtoimposetheideasofonegenerationuponanother.53This problem is inherent in expert system designin the law
andinotherdomains. Therearedangers,forexample,intheuseof a legal expert system byjudges. Stone considers the use ofpredictivetechniquesinthelawandwarnsthat:
. . . reliance at thejudgment seat on new predictive techniqueswouldseriouslythreatenthejudgescentralconcernwithjustice.Foriftheresultsthuspredictedforhimdoaffirmativelyguidehiminpresentdecisions,eachjudgewilltendtovotesomewhatmoreconsistentlywithhispastrecord. Themarginofdeviationwouldaccordinglydisappearindeferencetopredictedpatterns,aidedbythehumantendencyto followthe lessagonizingbecausealreadytroddenpath. . . 54
Judges,Stonesays,haveadutytostrivewholeheartedlyforjusticeatthemomentofjudgment.55 Althoughanexpertsystemmaybe of some use tojudges of lower courts, there is a critical borderbetweenamachineservingthelegalorderandthedangersofsubversionofthatorder.
For whenever an appellatejudge faces the duty to dojustice inthis sense, he must address himself to it with his own presentexperience and insights. It would be a corruption ofjustice forhim to shortcut this duty by resting on predictions of his futuredecisionsbasedonhisownpastbehaviorstillmoresoifthebasisistheaveragepastbehaviorofagroupofjudges.56
So, as Stone points out, the pioneers and experts of the newtechniques must face the limits of the contributions they canmake.57
1.2.5 ClearrulesandclearcasesH.L.A.Hartwasthemostfamousofthepositivistlegaltheorists.Hismajorwork,TheConceptofLaw,waspublishedin1961. Hartrealizes that because the law is expressed in natural language, it
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issubjecttoconsiderablesemantic indeterminacy. Thishetermsthe open texture of law. However, he claims that it is possibleto use rules deductively to solve clear cases: that is those inwhich there is general agreement that they fall within the scopeofarule.58 Healsocontendsthat:
. . . theresultoftheEnglishsystemofprecedenthasbeentoproduce,by itsuse,abodyofrulesofwhichavastnumber,ofbothmajorandminorimportance,areasdeterminateasanystatutoryrule. Theycannowonlybealteredbystatute,asthecourtsthemselvesoftendeclareincaseswherethemeritsseemtoruncountertotherequirementsoftheestablishedprecedents.59AsSusskindwrites,oneramificationofHartsanalysisisthat:. . . allexpertsystemsinlawwhoseinferenceproceduresaresolelydeductive will function exclusively in the clear case domain, andwillbeofnoaidinthesolvingofproblemsofthepenumbra.60
But what constitutes a clear case is itself far from clear. AsHartconcedes:
. . . it isamatterofsomedifficultytogiveanexhaustiveaccountofwhatmakesaclearcaseclearormakesageneralruleobviousanduniquelyapplicabletoaparticularcase.61Molesdisputestheveryexistenceofclearrulesandclearcases.
He performsa detailed analysis oftheapplicationofan exampleofanostensiblyclearrule inaBritishstatute: aprovisionwhichprescribesthecircumstances inwhichan injunctionshouldbe issued in domestic violence cases.62 He summarizes the effect ofthreecasesasfollows:
(1)BeforeB v. B63 weareconcernedwithastatutoryprovisionwhichonitsfaceappearstobeclearandcomprehensible(atleastto non-lawyers) and it would appear that an injunction shouldissueincasessuchasthosewehavelookedat.
(2) After Cantliff,64 the provision has been considered twiceby the [English] Court of Appeal within two weeks. All of thesixjudges who considered the matter are in agreement that theinjunctionshouldnotissueandthattheruleisclear.
(3)Thematter is furtherconsideredbyaspeciallyconstitutedCourt of Appeal of five,65 who decide that the rule is clear, butdifferentfromthatin(2),andthattheinjunctionshouldissue.66
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Moles also analyses thejudicial application of the rule of precedentwhich, with this statutory rule, must be regarded asamongsttheclearestavailabletous67todemonstratethatourexperience of the legal system bears little relationship to Hartsaccountofit.68
Leithdevelopedalegalexpertsystemwhichoperatedonclearrulesinthelaw.69 Helaterrecanted,sayingthat:
. . . thevery ideaofaclearruleis inherentlyconfusingand isnotobservableintherealoperationofthejudicialprocess. . . judicialcreativity is not an aberation [sic] of the legal process, but (asMoles. . . suggests),theveryheartofthelaw.70
Asisexplainedbelow,71 manyexpertsystemdesignershaveadoptedaviewofthelawthatallowsforclearrulesandclearcaseswithout considering the possibility that the law may not be likethat at all. 1.2.6 LegalrealismandrulescepticismInthe1920sand1930s,amovementcalledlegalrealismdevelopedin America.72 Realists rejected the importance that mechanical
jurisprudenceplacedonrules. However,therulescepticismoftheAmerican Realists is meek by comparison with the strong indeterminacythesis. DrahosandParkerexplainthat:
According to Karl Llewellyn a characteristic feature of Realismwas the rejection of simple (by which he meant general) rulesandthesubstitutionofmoredetailedclassificatoryschemeswhichbettercapturedthespecificnatureofjudicialrule-making. . . OnLlewellyns account, rule scepticism emerges as a set of doubtsabouttheveracityoflegalactorsclaimstobefollowingthelegalrulestheysaytheyare. This is notrulescepticism inthestrongsense of denying the existence of rules, however. Legal actorsmaysimplybefollowingsomeotherrules. TherulescepticismofAmericanRealismcouldperhapsbemoreaccuratelydescribedasrulecynicism.73Kripke, by contrast, is a true rule sceptic. His argument is
an example of the Wittgensteinian Paradox.74 Consider the twofunctionsplus(+)andquus(). The+functionisthemathematicalfunction,addition. Thefunctionisdefinedasfollows:
x+y, ifx, y
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1.2 Legalexpertsystems 15
SupposethatKripkehasused+inthepast,butalwayswithvaluesofxandysmallerthan57. Heperformsthecomputation68+57andgetsaresultof125. Yetitcouldbesaidthatwhenhethoughthewasusingtheplusfunctioninthepast,hewasinfactusingquus. AsKripkeexplains:
. . . inthisnewinstance,IshouldapplytheverysamefunctionorrulethatIappliedsomanytimes inthepast. Butwho istosaywhat function this was? In the past I gave myself only a finitenumberofexamplesinstantiatingthisfunction. Soperhapsinthepast I used plus and + to denote . . . quus . . . Who is to saythat[]isnotthefunctionIpreviouslymeantby+?75
There is nojustification for Kripke answering 125 rather than 5.Thereisnowayofdetermining(fromhispastbehaviourevenhispastthoughts)whetherbyplusKripkemeant+or. Rulesarederivedfromafinitenumberofexamples;foranygivenrule,thereisalwaysanalternativerulewhichalsoexplainsthoseexamples.
Mathematicians could counter that the meaning of + is welldefined. ButKripkearguesthat:
. . . scepticismaboutarithmeticshouldnotbetakentobeinquestion: wemayassume,ifwewish,that68+57is 125. . . Icannotdoubtcoherentlythatplus,asInowuseit,denotesplus! PerhapsIcannot. . . doubtthisaboutmypresent usage. ButIcandoubtthatmypast usageofplusdenotedplus. . .
. . . Thereisnoobjectivefactthatweallmeanadditionby+,oreventhatagivenindividualdoesthatexplainsouragreementin particular cases. Rather our license to say of each other thatwemeanadditionby+ispartofalanguagegamethatsustainsitselfonlybecauseofthebrutefactthatwegenerallyagree.76DrahosandParkerwritethat:Theconsequencesofthisargument,ifvalid,areshattering. Rulesturnouttobenomorethanleapsinthedarkandthewholenotionofrulefollowingseems illusory.77The implications of Kripkes argument have been realized by
legaltheorists.78 AsDrahosandParkerpointout:Saying that there are no rules to follow, only social practices,means that propositions about the law are potentially open towildfluctuations. Theargumentalsoputspaidtoanypossibilityofacorrespondencetheoryoftruth inlaw.79
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Theyproposeasolutiontothisproblem:TheKripkeanargumentdoesnotpreventpeoplefromsaying thatthey are following rule X. Rather it stops them from being abletojustifytheexistenceofthatrulebyreferencetosomeobjectivemeaning. Thisstillleavesthepractice,asopposedtothejustification,ofsuccessfulrulefollowingtobeaccountedfor.80
Their solution is to view the law as a set of rules and conventions: atypeofruleusedtofixorinterpretthemeaningofotherrules.
81Theyclaimthereisadistinctionbetweenruleknowledgeand rule understanding, the latter being a matter of absorbing
conventionsrelatingtoruleuse.82 Alawyerrequiresknowledgeoftherules,andunderstandingastohowtoapplythoserulesproperly. DrahosandParkerarguethattheproblemsfacingdesignersof legal expert systems flow from the difficulties of representingrule understanding rather than rule knowledge.83 Rules can beused to represent rule knowledge; the problem is how to represent with tolerable accuracy . . . conventions which confer ruleunderstanding.84
Buttheyconcedethat,aswithotherrules,conventionshavetorunthegauntletofscepticism.85
1.2.7 Ajurisprudentialconsensus?The only major examination of the role ofjurisprudence in thedevelopment of legal expertsystems isSusskinds 1987 bookExpert Systems in Law: A Jurisprudential Inquiry.86 As discussedabove,87 hearguesthatallexpertsystemsmustconformtosome
jurisprudentialtheory.Healsosetsouttofindconsensusinjurisprudentialtheory. As
thereisfartoomuchliteratureinthefieldforonepersontocoverit all, he limits his choice of material: the vast majority ofsources that he uses are British analyticaljurisprudential writingssincethemid-1950sandearly1960s,theimpetusforwhich,he concedes, was derived very largely from the publications ofH.L.A.Hart.88
Susskindconcludesthattherearenotheoreticalobstacles,fromthe point of view ofjurisprudence, to the development of rule-based expert systems in law of limited scope.89 He also claims
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1.2 Legalexpertsystems 17
that the divergence of views withinjurisprudence has been overstated because legal theorists tend to focus on the differences.He claims that there is a jurisprudential consensus, albeit ofmundaneandlimitedapplication.90
Susskind provided the theoreticaljustification for not only hisowndevelopmentwork,91 butformuchofthesubsequentworkofother developers of legal expert systems. He could also be saidtohaveprovided,retrospectively,legaltheoreticaljustificationformostoftheworkonrule-basedexpertsystemsthatprecededhisbook.
However,Susskindsapproachtojurisprudenceisfundamentallyflawed. AsMolespointsout:[Susskind] said that he would carry out a survey of thejurisprudential literature. Heacknowledged, ofcourse, that itwouldnotbe possible to survey the whole of thejurisprudential literature.Infact,hedeterminedthatlawwasasystemofrulesbysurveyingonlythosewhoseavowedpositionwasbasedonthefactthatthe lawwas asystemofrules. . .
I would venture to suggest that this is in fact a misuse of thesurveytechnique. . . SusskindwasperfectlyfamiliarwiththeworkofHartandhisfollowers,andwaswellable,therefore,tofindanynumberofbooksandarticleswhichsupportedthelawasrulesview. Hethendevelopedhisposition. . . onthebasisofwhatthispurportedconsensus withinjurisprudencehadtosay.
. . . Of course, Susskind was telling certain sections of the AIand Law community what they wanted to hear, and hence theirenthusiasmfor it.92
Moles also notes Susskinds admission that the most rigorousof these writings constituted the source materials with greatestpotential given the overall purpose of the project.93 Becausethe first objective of Susskinds work was to design, develop andimplement an expert system in law,94 Moles cites this admissionasevidencethatSusskindprejudgedhissurvey.
Inthe lightofthiscriticism, it isironictonoteSusskindsowncautionthat:. . . alittlejurisprudentialknowledgecanbeadangerousthing! Itistemptingforthejurisprudentialneophytetobecomeanardentdevoteeofaparticularschoolofthoughtwithin legaltheoryandto go on from there to implement all and only the teachings ofthatschool. Thiscourseofactionshouldbeavoidedatallcosts.
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Familiarity with a wide range of works should be achieved priortocommitmenttoanyparticularjurisprudentialposture.95Clark,anothercriticofSusskind,saysthat:Theshortcomingsof[his]bookcoincidewiththelimitsofpositivistlegaltheory,andeventhensomedoubtmustremainastowhetherexpert systems in law mark a revival of the kind of mechanical
jurisprudencewhichHartopposedsovigorouslyfromwithintheconfinesofpositivistlegalthought.96
ButthestrongestcriticismofSusskindcomesfromLeith:. . . [Susskind]believesthathecancometosomesortofcompromise with the various theoretical positions taken by the renownedthinkersofthefieldandproduceageneraltheory(anindication,Imightsuggest,of[his]poortheoreticalconceptions). . .
. . . Susskindseesjurisprudenceasprovidingavarietyoftheoreticalmodelswhichcanbemodelledmathematicallyandtranslatedintocomputerprograms.
. . . [O]f necessity formal specification requires a formalisationoflaw;therecanbenoinformalmodelswhicharemysteriouslyformalisedintoacomputermodel. . .
. . . Therefore, in order to use formal specifications, Susskindmust provide a formal specification of law which can then be incorporated intotherule-formatofacomputerprogram . . . And,ofcourse,formalspecificationsof lawarerenownedfortheirtheoretical and practical inadequacy. Legal formalism can, surely,hardlybethecompromisehewishesmightarisefromtheconflictingpositionsofKelsen,Hart,Dworkinetal.97
. . . [I]fhereallydoesbelievethathisinformaltheoreticalmodelscanbetransformedintoformaltheoreticalmodelswithoutlossoftheir informal attributes, then I must suggest that he has reallylittleunderstandingofthedisciplineofcomputerscience.98Susskindsclaim to have found a consensus injurisprudence
even one of mundane and limited applicationis absurd. Asshown above,99 the views of just two jurisprudents (Hart andMoles) are completely irreconcilable. Similarly, Harts views aretotallyatoddswiththoseofKripke.100 Susskindstateshistheory,anddevelopsanexpertsystemwhichconformstothattheory. Hismistakeistoclaimthathistheoryisdefinitive,inthatitrepresentsajurisprudentialconsensus.
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1.3 JurimetricsandthebehaviouristsAsmentionedabove,
101thetermjurimetricswascoinedbyLoevinger. He defines jurimetrics as the study of law and legal
problems by scientific methods and concepts, the employment ofscienceinlawtotheextentthatitisapplicableoradaptable.102Loevingerisneitheramechanicaljurisprudentnorapositivist:
Tobeginwithwe must beclearthat science offers us neitherultimate nor certain answers to legal problems. The dream thatsciencemightsomedaytelluswhichofseveralcompetinginterestsis the more important is a vain one. Science essays no such answersinanyfield. Sciencedoesnotassignsocialorethicalvalues.Science may, indeed, provide data from which social or ethical
judgmentsmaybemade;butthejudgmentswillremainwithman. . .
Thereisnoprospectofanyprocessthatwillprecludeconsiderationofsocialdesirabilityorwisdom. Theopportunitywillalwaysbe available to argue that precedent should not be followed, andthat considerations of policy, or expediency, require a differentruleoraspecialresult. . . . . . Sciencedoesnotandwillnotofferusanylawmachinesthatgiveautomaticanswerstospecificquestionsputtothem,whetheras to particular cases or as to ultimate legal issues such as therelative importance of interests that may be in conflict. By thesame token, science will provide us with no formulae or calculusthatwillgiveuscertaintyeitherofprediction,analysisoranswerstoultimatequestionssuchaswhich interest istobepreferredorwhichdesirehasgreatersocialvalue.103
Althoughthesecommentsareeminentlyreasonable,someofLoevingersturnsofphraseareexasperating. In1949heclaimedthatputtingthelawonarationalbasiswastheindispensableconditionofthesurvivalofthehumanrace.104 Inthelightofsucharidiculousstatement,andafterhistrenchantcriticismofthevalueofjurisprudence (quoted above105), it is not surprising that, asGardnersays:
The attitudes Loevinger and his colleagues expressed were neveradopted by the legal profession generally . . . As a movementwithin the legal profession,jurimetrics has not been much heardfromsincetheearly1970s.106
Nevertheless,someoftheworkofhiscolleagues,applyingvariousstatistical and logical techniques to legal analysis, is worthy ofcommenthere.107
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1.3.1 KortKort
uses
mathematical
expressions
to
represent
American
judicial
decisions.108 Heidentifiesattributeswhichareofimportanceandrepresentsdecidedcasesinthefollowingform:
n
Aijwi =Vji=1
where n is the number of attributes, Aij is the value of the ithattribute for thejth case (attribute values being 0 or 1), wi isthe weight of the ith attribute, andVj is the number of votes of
judgesfavourabletothepartyseekingredressinthejthcase. Thisapproachisjustifiedonthebasisthatthedecisionsofsplitcourtsdonotnecessarilyconstitutetwooppositeextremes,butrepresentcertaindegreesofsupportforoneparty.109
By solving these simultaneous equations, weights are obtainedfor the attributes. The sum of the weights of those attributespresent in the instant case is, according to Kort, the number oflikelyjudicialvotesinfavourofthepartyseekingredress.1.3.2 LawlorLawlor uses logical expressions to represent previously decidedcases.110 He analyses right-to-counsel cases heard before the USSupremeCourtover30years, andfindsthat inallofthesecaseseachjustice behaved consistently with his own personal staredecisis. He identifies legally significant attributes and builds alogical expressionwhichrepresentsthebehaviourofeachjustice.Aprogramusestheselogicalexpressionstopredictthelikelyoutcome,givenacompositionoftheCourtspecifiedbytheuser.
LawlorssystemsuccessfullypredictedtheUS SupremeCourtsoverrulingofBettsv.Brady111 inGideonv.Wainwright.112 Butitpredicteda5:4majority;theSupremeCourtsdecisionwasunanimous.
Applyingtraditionalstaredecisis(i.e.consideringthecourtasawhole,ratherthanthedecisionsofindividualjustices)Lawlorssystem did not predict the Supreme Courts change. Given thesamecases,Kortsapproachdidnotpredictthechangeeither.
Thisfailuredrawscriticismfromthosewhodisagreewithsuchalogarithmicapproachtojustice.113 Wienercomplainsthatadvocates ofthecomputerresttheirargumentsonanassumption
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1.3 Legalexpertsystems 21
thatcourtswilladheretothedoctrineofstaredecisis,whichdoesnotalwayshold.114
Indefenceofthebehaviourists,KaytonreferstotheirfailuretopredictthedecisioninGideonv.Wainwright andwrites:Shouldwehaveexpectedotherwise? Ofcoursenot! Areversal isbydefinition a logical inconsistency. That which by stare decisishadbeencalledblackisnowcalledwhite.115
Thedevelopersofthesepredictionsystemsacceptthattheyrelyonthedoctrineofprecedent. Hence,areversalofpreviousauthoritywillalwaysbebeyondthepredictivecapacityofthesesystemsasitisbeyondthepredictivecapacityofmostlawyers.1.3.3 NagelandSchubertNagel and Schubert116 examine the personal attitudes of US Supreme Courtjustices towards various political and economic relations, and claim that these off-the-bench attitudes (as Nagelcalls
them)
affect
the
justices
decision-making.
Correlationswere. . . madebetweenresponsestospecificitemsandvariousdecisionalpropensities. Forexample,therewasahighandstatistically significant correlation between disagreeing with [onequestionnaireitem](Ourtreatmentofcriminalsistooharsh;weshould try to cure, not to punish them) and being above theaverageofonescourtwithregardtotheproportionoftimesonevotedfortheprosecutionincriminalcases. Off-the-benchjudicialattitudes
thus
do
seem
to
correlate
in
a
meaningful
way
with
on-the-benchjudicialdecisions.117
1.3.4 Haar,SawyerandCummingsIn the mid-1970s Haar, Sawyer and Cummings made use of regression analysis to build a predictive model for zoning amendment cases in Connecticut.118 Regression analysis is a statisticaltechnique for analyzing the relationship of a set of independentvariablestoadependentvariable. ForHaaretal.thedependentvariableistheoutcomeofthecases,theindependentvariablesareattributes.
Theyidentify167attributeswhichappearedtobeimportantto the courts, 40 of which were deemed significant using a 2(chi-square)test forassociation. This istoomanytouse inaregressionanalysis,119 soHaaretal.employtwodifferentmethods
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toreducethisnumberfurther: groupingattributesonthebasisofexperience,knowledge,andintuition,120 andfactoranalysis.1.3.5 TheroleofpredictionThebehaviouristspredictiveresearchhasbeencriticizedbecausethey do not attempt to model legal reasoning.121 But, in notso doing, the behaviouristsjust reflect the influence upon themof the American Realists. They adopt Holmess analysis thatfor any individual the law is simply a prediction of the way inwhich
the
public
force
possessed
by
the
government
will
act
upon
him.122 Loevingerclaimsthatsomemethodoflegalpredictionisindispensable;123 Lawlor says that the ultimate goal of all scientificmethodsisreliablepredictionoffutureeventsand[r]eliableprediction is also one of the ultimate goals of law.124 Susskind(certainlynobehaviourist)alsostressestheimportanceofthepredictionofjudicialdecisions.125
Tapperwritesthat:Although the statistical techniques employed by some of theseworkershavebeencriticized,therecanbenorealdoubtthatthisworkprovidesasuccessfulapproachtotheanalysisofthedecisionswhichhavebeenreached inthepast,andat leastassatisfactorya method of predicting future decisions as can be arrived at bynativewitandunaidedintuition.126
However,hecriticizestheconclusionsthathavebeendrawnusingthesetechniques:
Either the behaviourist is to content himself with observing theobjectivephenomena,inwhichcasehecanconcludenothingastomotivation, or he is to ascribe motivation to the phenomena, inwhich case he ceases to be objective. It is precisely at the pointat which decisions of the [US] Supreme Court, for example, arecharacterizedaspro-civillibertiesoranti-labourthatdoubtsariseastotherealobjectivityofthestudies.
The same general line of argument may be advanced againstthefact-orientedapproach . . . Herethepointatwhichthestudyloses itsobjectivity is inthecharacterizationofthe factspresentinthecase.127
(Althoughthismaybeavalidcriticismofabehaviouristicstudy,itisnotanargumentagainsttheuseofpredictivetechniqueswherethe characterization of facts has been performedsubjectively,admittedlybyalegalexpert,asisdoneforSHYSTER.)
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1.3 Legalexpertsystems 23
Gardnerisalsocriticalofthejurimetricprograms:. . .
programs,
done
from
a
political
science
viewpoint
rather
than
a legal one, in which the data concern legally irrelevant matterssuchastheideologyandsocialbackgroundofindividualjudges.128
By legally irrelevant matters Gardner means those matters towhichjudges do notand/or should notexplicitly have regardwhencomingtotheirdecisions. Butifasystemisdesignedtopredictdecisionsthenanyattributewhichassistsinpredictionshouldbeincludedregardlessofwhetherregardought tobehadtothatattribute. These legally irrelevant matters are not necessarilyirrelevanttothepredictionofjudicialdecisions.
Stonedismissesconcernaboutjurimetricprediction: thebehavioralists [sic] may have no conscious designs on the integrityof the decisional process. Thejudgment ofjustice may be of noconcerntothem.129
Hedefinesthejudgmentofjusticebyreferencetoasituationwhereajudgemakesadecisionwhich:
. . . does not merely declare the existing law but decides whatjustice requires that the law should be. (. . . [W]e include tacitlyhere the reversal of earlier decisions, that is, creative decisionswhich unsettle and resettle law: this is afortiori creative.) Itis this kind of creative judgment which we have here termed a
judgmentofjustice.130Thebehaviouristsare,Stonesays:
. . . onlyobserverslookingatwhathasalreadybeen done injudgment. And when in the course of prediction they turn theirattention to futurejudgments, it is to ask not what thejudgeshoulddotofurtherjusticebutonlywhatkindofdecisionhewillgive if he acts consistently with values attributed to him on thebasisofhispastdecisions.131
Inotherwords,thebehaviouristsworkattemptedtobepredictivenotnormative.
When a lawyer gives advice, she/he is expected to make somepredictionastothelikelyresult. Thispredictionneednotbeemphatic: it may be no more than a tentative statement about thestrengthofapersons legalposition. Hence, legalexpertsystemsshould have some degree of predictive capacity. Like the behaviourists research, a legal expert systems predictive power is a
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24 Apragmatic legalexpertsystem 1.4
projectionbasedonpastcases. There isandcanbenoallowance for changing social mores. This is not a serious limitationupon such a systems utility: predicting ajudge-made change inthelaw isbeyondallbuttheverybestlawyers.
However, as discussed below,132 thejustification that a legalexpertsystemprovidesforitspredictionisalsoimportant.1.4 Rule-basedsystems
Thereare
many
examples
of
rule-based
legal
expert
systems,
the
most importantofwhich are discussed in detailbelow: theworkof McCarty; Bench-Capon, Kowalski and Sergot; Gardner; andSusskind.
Thefirstproposalforarule-basedlegalexpertsystemwasmadebyBuchananandHeadrick in1970. Theycomplainedthat interdisciplinary work between lawyers and computer scientists hadfloundered on the misconceptions that each has of the othersdiscipline,133 andsuggestedthatthecomputermodellingoflegalreasoningwouldbeafruitfulareaforresearch.134
Their proposal asserts that [i]n the absence of any reason tospeculate on how they carry on their work, [lawyers] now apply complex sets of rules without being aware ofthe rules themselves.135 Theymakenoreferencetojurisprudentialwriting,butthey do make it clear that their approach is based upon two assumptionsabouthumanproblem-solvingingeneral: (1)problemscanbebrokendownintoasetofsubproblems,and(2)thesolutiontoanysubproblemrequiresaseriesofdecisionsthataregovernedbydecisionrules.136
Theliteratureisrepletewithexamplesofprojectsinwhichtheassumption that lawyers work with rules is unstated and/or unsupported. MaggsanddeBessonet,forexample,tacitlymakethisassumption.137 The law, they claim, can be expressed as rulesusingpropositionalcalculus. Aprogramwhich implementstheserulescouldanswerquestions fromauser, andallowthecheckingof statute law for redundancy and contradiction. (It is not clearwhatrolecaselawplaysintheirsystem,orindeedintheirmodelofthelaw.)
Popp and Schlinks JUDITH system138 uses rules to representparts of the German Civil Code. The principles behind JUDITHarestrikinglysimilartothoseoftheMYCIN system(anexpertsystem dealing with bacterial infections)139so similar that, its
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1.4 Legalexpertsystems 25
developers claim, it would be possible to create a legal knowledgebaseforMYCINandamedicalknowledgebaseforJUDITH.140Michaelsen and Michies TAXADVISOR system141 is implementedusing MYCIN.142 TAXADVISOR is designed to assist lawyers toadviseclientsontaxationandestateplanning.143
Meldmanssystemusestwodifferentkindsofrules: generalruleswhich definetheelements ofthe claim, andspecificrulesextracted fromcases.144 Things andrelations areusedtorepresenttheeveryday world of human affairs,145 and are classified hierarchically intocategories. Afact comprisestwothingsandarelationbetween them; facts are assembled into situations. These situations are compared with the situation of the instant case, andthe system determines the extent to which the instant case fallswithin or near the law of intentional torts (e.g. assault and battery).
WatermanandPetersonsLDSsystem146 isarule-basedsystemforthefieldofproductliability. Itdoesnotdeterminewhetherliability exists, but is designed to assist legal experts in settlingproduct liability cases. LDS is a typical example of a systemwhichdevelopedwithoutanylegaltheoreticaljustification. Afteradmitting that there is no deep model of the legal process,147Watermanandhiscolleaguesproceedontheunstatedassumptionthatanysuchmodelmustinvolverules:
Onemightexpectthatthelargebodyoflegalrulesandregulationsthat have been accumulated and formalized in the legal domainwould make expert system development easier. Unfortunately,this is not the case. Instead, this characteristic of the domain,having rules that already exist, has led to trouble . . . First, theformal rules thatdefineand regulate legal activity are oftenambiguous, contradictory and incomplete. Andsecond, there existsa body of informal rules or procedures about how to access, interpret and use the formal rules. Without these informal rulesthe formal rules can not be used in any efficient or cost-effectiveway.148
Thisbodyofrules,theywrite,needstobemappedintocode149beforealegalexpertsystemcanbebuilt.
BingsSARA system150 isdesignedtoanalysediscretionarydecisions. It uses rules to represent legal norms: some strict andsome discretionary. These discretionary norms are weighted usingcorrelationtechniques. SARA allowsa lawyertobackuphisqualitativelegalreasoningbyquantitative indications.151
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StampersLEGOL language152 alsousesrulestorepresent legalnorms. PattisonandCiesielskiusearule-basedsystemtoreviewcontracts.
153SoftLaws STATUTE, acommercially successful system,usesrulestorepresentstatutes,regulationsanddepartmental
guidelinesintaxation,socialsecurityandveteransaffairslaw.1541.4.1 McCartyMcCartyhasbeendescribedasthefatherofAIandlaw.155 HisTAXMAN project156 isconcernedwiththedevelopmentofacomputationaltheoryoflegalreasoning,usingcorporatetaxlawasanexperimentalproblemdomain.
Heclaimsthatacomputer-basedlegalconsultationsystemmustbe able to represent the facts, at some comfortable level ofabstraction, and the law, which would consist of a system ofconcepts and rules. These concepts and rules are relativelyabstract(i.e.theysubsumelargeclassesof lower-level factualdescriptions),andtheyhavenormativeimplications(i.e.theyspecifywhich
actions
are
permitted
and
which
are
obligatory).
Legalanalysis,initssimplestform,wouldthenbeaprocessofapplyingthelawtothefacts. Putthisway,theparadigmseemsto be an ideal candidate for an artificial intelligence approach:the facts would be represented in a lower-level semantic network, perhaps; the law would be represented in a higher-levelsemantic description; and the process of legal analysis would berepresentedbyapattern-matchingroutine.157
However, McCarty concedes, the representation of facts in sucha system is more difficult than in other expert systems, becausethe facts of a legal case typically involve all the complexities ofdailylife: humanactions,beliefs,intentions,motivations,etc.158Evenifthefactscanberepresented,hewrites,theruleswilloftenbeproblematic:
Some rules, usually those embodied in statutes, have a preciselogical structure, and this makes them amenable to the existingartificial intelligencetechniques. But it isacommonplaceamonglawyersthatthemostimportantlegalrulesdonothavethisformat all: instead they are said to have an open texture; theirboundaries are not fixed, but are constructed and modifiedas they are applied to particular factual situations. A sophisticated legal consultation system would not be able to ignore thesecomplexities,butwouldhavetoaddressthemdirectly.159
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1.4 Legalexpertsystems 27
McCarty also makes the startling claim that the simplestproblemsforfirst-yearlawstudentsarethehardestforanAIsystembecausethestudentdrawsuponordinaryhumanexperience:
Paradoxically, the cases that are most tractable for an artificialintelligence system are those cases, usually involving commercialandcorporatematters,whichalawyerfindsmostcomplex. Thereis a simple reason why this is so. A mature legal system in anindustrializeddemocracy is composed of many levelsof legal abstractions. . . Becauseoftheirtechnicalcomplexity,thelegalrulesatthetoplevelsofthisconceptualhierarchyaredifficultformostlawyerstocomprehend,butthiswouldbenoobstacleforanartificialintelligencesystem.160McCartychosetheareaoftaxlawforhissystembecausecom
mercial abstractions, in fact, are artificial and formal systemsthemselves,drainedofmuchofthecontentoftheordinaryworldand, by legal standards, well structured.161 The field of corporate tax law, he says, is very near the apex of the hierarchy ofcommercial abstractions162whatever that means, commentsMoles.163InTAXMANI,McCartysfirstprototypesystem,thebasicfactsofacorporatecasearecapturedinarelativelystraightforwardrepresentation(e.g.acorporation issuessecurities). Belowthis levelis an expanded representation of the meaning of various entities(e.g. a security interest) in terms of their component rights andobligations.
Above
this
levelpresumably
above
both
levels,
althoughthisisnotmadeclearisthelaw(statutoryruleswhich
classifytransactionsastaxableornon-taxableetc.).164McCartyfoundthat,althoughtherulesarecomplex,theunder
lyingrepresentationsaremanageable. Heconcludesfromhisearlywork that the construction of an expert consultation system inthisareaofthelawisafeasibleproposition.165
McCarty sees the development of legal expert systems as anopportunity
to
contribute
to
jurisprudence.
Although
the
jurisprudential literature includes many illuminating examples and
manyvaluableinsightsaboutthestructureanddynamicsoflegalconcepts,hecomplainsthattakenasawholeitisnotoriouslyimprecise.166
TheTAXMANsystemaddsastrongdoseofprecisionandrigortothesediscussionsoflinguisticandconceptualproblems. Itscritical
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28 Apragmatic legalexpertsystem 1.4
task is to clarify the concepts of corporate reorganization law insuchawaythattheycanberepresentedincomputerprograms.167Molesisverycriticalofrule-basedexpertsystemsdesigners,and
McCartyinparticular. McCartytakesapositivistapproachtothelaw,andMolescomplainsthat:
Thecomputerscientistshavetakenthede-humanizingaspectsofmodernpositivismtotheirextreme. . . .
Thecomputerscientists,encouragedbythemodernpositivists,fail to recognize the point which Austin168 correctly emphasizedthroughout his workthat law, positive morality and ethics areinseparablyconnectedpartsofavastorganicwhole.169
MostdamningisMolessstatementthat:Thesadthingisthat[McCarty]hasnotshowntheslightestawarenessofthenatureofthelegalenterprise. Farfromhavingemphasizedanydifficulties,heshowsthathesimplydoesnotunderstandwhattheyare.170McCarty
does
identify
two
major
limitations
to
the
approach
takeninTAXMANI. Firstly,heconcedesthatthefactualdescriptions, although manageable in the corporate domain, would betoo complex in (for example) the average contract or tort problem. Secondly,thehigher-levelconceptualrepresentationsarenotadequate for all domains becausejudicially created concepts areincurably open-textured, have a dynamic structure with the capacity to evolve and adapt to new situations, and the evolutionof these concepts is governed by a sense of purpose.171 Havingrecognized these problems, McCarty set out to solve them withTAXMANII.TAXMANII172 usesprototypesanddeformationstorepresentalegalconceptbyspecifyingtheprerequisiteconditionsforthatconcept,asetofcases(realandhypothetical) inwhichthatconceptdoes or does not apply, and a set of transformations for gettingfrom one case to another. If a given case (representing a legalconcept)canbetransformedintotheinstantcase,whilestillsatisfyingtheprerequisiteconditions fortheconcept,then itcanbeusedinargumentasanexampleofthatconcept.
AshleyseesMcCartysworkasasignificantadvance,butpointstoseveralshortcomingsofTAXMANII:
Thework is largelyanexerciseinknowledgerepresentation. Mc-Cartydoesnotset forthacontrolorprocessmodelthat clarifies
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1.4 Legalexpertsystems 29
howaprogramwouldactuallygeneratealegalargument. . . Thereportedresearch involvesahandsimulationofthearguments inone
US
Supreme
Court
case
173and
work
done
on
hand
simulations
ofseveralsubsequentcases.
. . . [TAXMAN II] has no mechanisms for comparing cases intermsofhowonpointtheyare,fordistinguishingcases,orselectingthebestprecedents. . .
McCartys model assumes a much neater domain than existsin law. He assumes that in reality, legal cases are consistentlyallocated as positive and negative exemplars of concepts. Theyarenot. Heassumesthatthereisanearmatchbetweenconceptsandthefeaturesofacasethatarerelevanttotheconcept. Thereisnot.174
McCartys definition of legal primitives has also been criticized.Moleswrites:
McCartyappearsnottoappreciatethatcorporations,securities,property, dividends and so on are not subsumed beneath thelaw, but are each the products of complex legal analysis. Thequestionofwhethercertaintransactionsaretaxableornot is intimatelytiedintothatlegalanalysis.175
Ashleymakesasimilarpoint:The problem with such primitives, if they are taken seriously asa means for definingconcepts, is thattheyassume what isto beshown. Farfrombeingaprimitive,thatsomeonehasarightoradutyinagivenfactsituationisanarguablelegalconclusionthatmustbejustifiedbycitingauthorities.176
1.4.2 Bench-Capon,KowalskiandSergotBench-Capon,Kowalski,Sergotandtheircolleaguesuseprogramswritten inthePROLOG languagetomodelstatutes.177 Theirapproach to legislation is the most extreme of all expert systemdevelopers, due to their attitude towards knowledge acquisition.Theywrite:
The formalisation of legislation by means of rules has almost allthecharacteristicsofanexpertsystem. Itdiffers,however,inoneimportantrespect. Inaclassicalexpertsystem,beforeknowledgecan be formalized, it has to be elicited from the subconscious ofan expert. Eliciting this knowledge is generally regarded as themain bottle-neck in the construction of expert systems. It is entirely absent, however, in the case of legislation which is already
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30 Apragmatic legalexpertsystem 1.4
formulatedandwrittendown. Thustheuseofexpertsystemtechniquesforrepresentinglegislationhasvirtuallyalltheadvantagesof
expert
systems
without
the
attendant
disadvantages
of
eliciting
theknowledge.178
This statement is nothing less than astounding. Even if it is acceptedthatstatutelawcanberepresentedusingPROLOGclauses,itisaboldclaim indeedtoassertthatconstructingthoseclausesrequires no expertise. As Moles says, [c]learly these researchersdo not distinguish between the writing (which is the legislation)andthemeaning ofthatwriting.179
Bench-Capon et al. have worked with several statutes. MostfamousistheirworkwiththeBritishNationalityAct1981(UK).180Consistent with their approach to knowledge acquisition, theirPROLOG representation of the British Nationality Act was implementedintwomonthsbyastudent,withoutanyexpertlegalassistance.181
They also represented the Supplementary Benefits Act 1976(UK)anditsregulationsusingasimilarmethod,andmadeasimilarclaimabouttheimportanceoflegalexpertise:
Forourproject,theaccuracyoftherepresentationwasnotacritical consideration at this [early] stage. Our formalisation couldtherefore be undertaken with no expert legal assistance . . . Ingeneral, accuracy of the formalisation is, of course, critical, particularly if one were constructing a representation to be used inpractice.182
Predictablyand correctlythis approach has been stronglycriticized. Molespointsoutthat:
Thisistoassume. . . thattheproblemwithregardtoaccuracyis merely a matter of changing the detail of content. It fails toappreciatethatanexpertmayhaveagreatmanyusefulthingstosayabouthowonegoesabouttheprocessof interpretation. Theexpertadvicewillthereforehaveimplicationsforthemethodbeingemployedandthewayinwhichtheknowledgeisstructured.183
KowalskiandSergotmakethisassumptionexplicit:Access to an expert adviser might well have changed the exactformoftherules inourprogram, but itwouldnot havechangedthemethodweusedtoformulateandcomputewiththerules.184
Buthowcantheypossiblybesure?
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1.4 Legalexpertsystems 31
Ontheneedforlegalexpertiseinthedevelopmentoflegalexpertsystems,SusskindquotesHayes-Roth,WatermanandLenat:
Itisveryeasytobedeludedintothinkingoneknowsagreatdealaboutthedomain. Remember: theexpertbecameoneonlyafteryearsoftrainingandexperience.185TheworkofBench-Caponetal.hasbeenmostvehementlycri
ticizedbyLeith. Hequotesthem:The formalisation of the British Nationality Act is an axiomatictheory similar, for example, to an axiomatisation of EuclideanGeometry. In principle, any logical consequence of the axiomatisationcanbegeneratedandtestedmechanically. . . 186
thencomments:Doesthissound likeawildclaim? Isuspectso. No lawyer,withwhom I have so far discussed Kowalskis legal work, has beenimpressed in the least: the common reply is, Surely he doesntbelieve that? And this is the rub. In AI research, funders areprepared to provide research funding for the most inane of ideaswithout appealing to those with some expertise in the area ofintelligencebeingresearched.187
1.4.3 GardnerTheaimofGardnersresearch188 isnottodevelopaprogramthatsolveslegalproblems:
Instead, the objective is to enable the program to recognize theissues a problem raises and to distinguish between those it hasenoughinformationtoresolveandthoseonwhichcompetenthumanjudgmentsmightdiffer. Towardthisendaheuristicdistinctionbetweenhardandeasyquestionsisproposed.189Her chosen domain is an aspect of the law of contract that is
dominated by case law: offer and acceptance. She claims that,although an area based on statute might seem easier for an AIprogram to handle, the reverse is true. Case law must be takeninto account in statutory areas too, and statutory interpretationraises itsownproblems. Hence, sheconcludes, [b]eginning fromstatutes therefore seems likelier to add a layer of complicationthantoremoveone.190 Susskindagrees: Gardner. . . isrightinrecognisingthatitisunrealistictofocusonstatuteattheexpenseofprecedent. Thereisalessonhereforallworkersinthefield.191
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32 Apragmatic legalexpertsystem 1.4
Gardners system has four different levels, the last of which isnot implemented. The network level is an augmented transitionnetworkwhichrepresentslegalstatesandevents. Therulelevel isasetofruleswhichoperateonobjectsatthefirstlevel. Theserulesaredefinitionsofthemajorconcepts192 inthelawofofferandacceptance. Thethirdlevelisasetofexampleswhichexplainthosepredicatesintherulelevelwhichareundefined,butwhoseresolutionisclear;thisincludes(non-legal)commonsenseknowledge.Gardner, citing the legal positivists, assumes that open texturedoesnotrenderallcaseshard:
Thefirstthreelevelsoftheprogramaredevotedtoidentifyingthehardquestions. Fromanoppositeviewpoint,thefirstthreelevelstrytoidentifytheeasyquestionsandresolvethem.193
Thefourth(unimplemented)levelwoulddealwiththehardquestions.
Susskindcommentsthat:Ultimately, the human expertise that Gardner tries to encapsulate in heuristic form is the ability to assess, in advance (in asense), whether a case does indeed raise easy or hard questions.Thiswillindicateifaconclusionmaybeinferredwithoutfurtheradoorwhetherhumanjudgementisrequired. Shemakesabraveattempt, but . . . I was left wondering about the generalisabilityof her ideas and their applicability in other, far more extensive,branchesoflaw.194
Ashley,too,iscriticalofGardnersapproach:. . . an attorney distinguishes hard from easy questions in termsof comparing the strengths of the best argument he or she canmakewiththebestargumentsanopponentcanmake. Gardnersprogramprovidesnomeasureforevaluatingthestrengthsofcompetingarguments. . .
Even if Gardners program evaluated case-based arguments, itcould not do so very realistically given the way cases are represented. Distinguishing, for example, is not possible because thereisnothingtodistinguish.195UnlikeMcCartyandBench-Caponetal.,Gardnerdoesconfront
theargumentsofthe(American)Realists:If legal realism is right, it appears to make the AI paradigm ofrule-basedexpertsystemsinappropriate,atleastwithanysimplemapping from legal rules to knowledge-base rules. There are
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1.4 Legalexpertsystems 33
severaldirectionsonemightgoinstead. Onedirectionwouldemphasizethe ideathat it is individualdecisions, not generalrules,that
have
authoritative
status
as
law.
With
this
emphasis,
one
might look for a method of reasoning from the decisions in pastcasestoa conclusion in a present case . . . 196 But this cannot bethewholestory. Ifitwere,whywouldpresent-daylawprofessors,thoroughly aware of the insights of realism, continue to expecttheirstudentstoknowrules?197
This isastrangeargument; itsaysmoreabouttheway inwhichthe law is taught than it does about whether a rule-based approach to the law is appropriate. (And it must be rememberedthat the American Realists were not true rule sceptics, as discussedabove.198)
Gardner identifies two other directions to take if legal realismisright: emphasizingthebehaviouristicsideoflegalrealism(e.g.thejurimetricsresearchdiscussedabove199),andathirddirectionwhichGardnerherselfadoptstoretainanimportantplaceforlegalrulesbuttoreinterprettheirsignificance.200 Sheclaimsthat:
Rulelikesentencescanbeunderstoodasusefulcognitiveconstructs,neededtofindorderin(orimposeorderupon)anunwieldymassofindividualdecisions. Oncearticulated,theycanprovideguidanceastohowfuturedecisionscanbekeptinsomeroughconformancewiththisorder;or,ifthearticulatedruleseemstobeabadrule,it can suggest a way of saying how the course of decisions oughttobechanged.201
Thisdoesnotreallyrepresentareinterpretationofthesignificanceof rules. Only the most ardent rule-follower would suggest thatruleswereanythingelse.
Gardner develops a rule-based model for offer and acceptancecases,butmakesthesignificantconcessionthat:
. . . a rule-based model of case law must be understood, like anyacademiclegalwriting,asasecondarysource. Theofficialsourcesare the decisions. There has never been agreement on what itwouldmeanforrulelikegeneralizationsfromdecisionstobebothaccurateandappropriate. Thus,thebasisforevenuncontroversialrulesremainsundefinedinlegaltheory.202
This isaninteresting,andquitepragmaticconcession,comingasitdoesfromsomeonewhoseworkhasbeencharacterizedasfairlyclearlypuristinnature.203
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34 Apragmatic legalexpertsystem 1.4
1.4.4 SusskindSusskinds
work
on
the
importance
of
jurisprudence
to
the
developmentoflegalexpertsystemsisdiscussedindetailabove.204 He
chose the Scottish law of divorce as his first experimental legaldomain.205 He has also been involved in the development of theLatentDamageSystem: alegalexpertsystemconcernedwiththetimeperiodswithinwhichclaimantsmaystartnegligenceproceedings where they have suffered latent damage or loss.206 CapperandSusskindclaimed in1988thatthiswasthefirst legal expertsystembuiltintheUK bylawyersforlawyers.207
Susskindbelievesthatstatutesandsomecasestheclearcasescan and should be represented using rules. With clear cases,heclaims,itispossibletodrawlegalconclusionsonthebasisofliteral interpretationsoftheformallegalsources.208 However:
. . . itshouldnotbetakenforgrantedthattheentirecommonlawsystem can be reduced to a collection of rules . . . Simpson hasforcefullycontendedthatsuchareductionistmodelmisrepresentsthecommonlawandisinconsistentwithitsdevelopment,content,andscope. . . 209
Other methods, he says, would be required in order to representcaseswhicharenotclear: methodswhichreasonwithuncertaintyanddrawprobabilisticallyphrasedconclusions.210 Yet,hecontends:
. . . althoughthecommonlawmaynotbesufficientlyrepresentedintermsofrules,itcannotbedoubtedthatitisinvariablypossible,desirable,andnecessaryto interpret individualcases inthe formofindividuatedrules.211
I doubt that it is possible, dispute that it is desirable, anddemonstratewith SHYSTERthat it isnotnecessarytorepresentcasesusingrules.1.4.5 KnowledgeacquisitionandrepresentationFeigenbaumwrotein1981that[t]herearemanyimportantproblemsofknowledgerepresentation,utilisation,andacquisitionthatmust be solved, but the acquisition problem is the most criticalbottleneck problem.212 As discussed above,213 Bench-Caponetal.claimthatthereisnosuchbottleneckforknowledgeacquisition from statute law because legislation is already formulated
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1.4 Legalexpertsystems 35
andwrittendown.214 However,thisdemonstratesaseriousmisunderstanding of the law. Knowledge acquisition is as much aprobleminthelegaldomain(statuteandcaselaw)asitisinanyother. Iproposeasolutiontothisproblem, at least in regard tocaselaw, inchapter2.
Inordertoavoidtheknowledgeacquisitionbottleneck,someresearchershaveexaminedthepossibilityofthemachine-processingofstatutes. Iftheonlyinputisthewordsofthestatuteitselfthenthisproblemisoneofunderstandingnaturallanguagearesearchfield inwhichresultshavenotfulfilledoriginalhopes.
Amorefeasibleapproachistoconvertthewordsofthestatuteintoamachine-readableform. Allenhasdevelopedonesuchformandclaimsthatifstatutesweredraftedusingthisform,notonlywouldtheautomaticlogicalanalysisoftheircontentsbepossible,but humans would be able to read and work with them moreeasily.215 Unless and until legislation is expressed in machine-readable forman extremely unlikely event, the desirability ofwhichisfarfromclearbuildersoflegalexpertsystemswhichdealwithstatute lawmustusehumanexpertisetoextractknowledgefromstatutes.
Theprocessofacquiringknowledgefromstatutesisusuallyseenas a process of writing rules. However, Shannon and Golshaniwarnthatdoingthisinanadhocfashionisunsatisfactorybecausetherulescannotbecheckedforcorrectness,andsuchanapproachmay lead to dissimilar rule formulations which do not work welltogether.216 Instead they recommend following precise and consistentmethods(likethoseofAllen)toformulaterules. This,theysay,wouldreducethescopefordissimilarruleformulations.217
Shannon and Golshanis belief that there is a correct interpretationofastatute issharedbymanyresearchers inthisfield.Inbelievingthis,theygoevenfurtherthanthelegalpositivistsonwhosetheoriesmuchoftheirresearch isbased.2181.4.6 FactrepresentationThe representation of legal facts in a rule-based systemindeedany expert systemis difficult. As with the representation ofstatutes,researchershavedevelopednormalizedformsforfactrepresentation. An example is deBessonet and Crosss atomicallynormalized form (ANF).219 Shannon and Gols
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