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Forensic Science

An Introduction

What is forensic science?

Science in service to the law

“…the application of science to those criminal and civil laws that are enforced by police agencies in the criminal justice system.”

Saferstein

What’s the key concept in FS?

Locard’s Exchange Principle (~1910)Whenever a criminal comes in contact with a person or object there is a cross-transfer of evidence.

What are the consequences of Locard’s Exchange Principle?

The perpetrator leaves evidence behind and also takes evidence away

The longer you wait before collecting evidence the less there is left

Every person at the crime scene including police investigators will contaminate it

Realistic?

What is Forensic Science Trying to Do?

The goal of Forensic Chemistry is to determine the provenance of a sample. Link it to a person, place or thing

prov·e·nance Pronunciation: 'präv-n&n(t)s, 'prä-v&-"nän(t)sFunction: nounEtymology: French, from provenir to come forth, originate, from Latin provenire, from pro- forth + venire to come -- more at PRO-, COME1 : ORIGIN, SOURCE2 : the history of ownership of a valued object or work of art or literature

Roles of the Forensic Scientist

Analyze physical evidence Provide expert testimony Train evidence collection units in

recognition, collection and preservation of evidence

Would you expect to see Gil Grissom collecting evidence at a crime scene?

The Crime Lab

Firearms

Photography

Voiceprint Analysis

Toxicology Evidence Collection

Latent Fingerprints

Polygraph

Documents

Biology

Physical Science

Crime Lab

Psychiatrist

Odontologist

EntomologistAnthropologist

Pathologist

Engineer

The Expert Witness

Trial judge must be satisfied that the expert Has skill or knowledge that will aid the

court in determining the truth Education (degrees, courses) Training (internship under experienced

practitioner) Experience (years on the job, publications,

professional societies)

Trial judge is the gatekeeper

The Expert Witness

An expert witness can testify as to his/her opinion of what the evidence indicates

A lay witness can only testify as to fact

What is the most common task a forensic scientist performs?

Take 5 minutes and discuss this in groups of 4 and then be ready to report out your reasoning.

The Expert Witness

Jury assigns weight to the expert’s opinions

Jury looks at Credentials Demeanor Whether material is presented simply

and clearly Jury is the trier of fact

Class vs. Individual Characteristics

Class characteristics: Many objects share the same set of

characteristics Shoe tread pattern, bullet caliber, shoe

size, overall pattern of a fingerprint Individual characteristics:

Unique to a single object Wear pattern on a shoe, striations on a

bullet, minutiae in fingerprints

Anthrax Letters

What types of evidence would you look for?

5 dead17 sickenedBeginning 9/18/2001

Apply your understanding:

What are class and individual characteristics of each of the possible types of evidence in the anthrax case?

Anthrax Letters Trace hair and fibers in envelope Ink analysis may reveal manufacturer DNA from stamp or envelope seal Cellophane tape ends match over four letters Paper examination may identify manufacturer Fingerprints Photocopier toner may reveal manufacturer Handwriting analysis shows four letters written by

same person Indented writing Bar codes for mail handling

Who did it?

Dr. Steven HatfillNow suing government

Dr. Bruce IvinsCommitted suicide July 2008

Analytic vs. Forensic ChemistrySimilarities

Analytic Wants to find composition of samples

Compounds Proportions in mixtures

Uses same instruments as forensic

Forensic Wants to find composition of samples

Compounds Proportions in mixtures

Uses same instruments as analytical

Admissibility: A Moving Target

Frye v. US (1923) Scientific evidence is admissible only if

it has gained general acceptance in the field

Rejected polygraph opinions Historical Perspective

Tennessee v. John Scopes (1925) The Monkey Trial

Admissibility: A Moving Target

Coppolino v. State of Florida (1968) Doctor accused of poisoning his wife

with succinylcholine chloride (muscle relaxant)

New and unique tests performed specifically for this case

Detected by-products of metabolism of poison (succinic acid)

Admissible if based on scientifically valid principles and techniques

Admissibility: A Moving Target

Federal Rule of Evidence 702 (1975) Approved by Congress More flexible general relevance test for

admissibility of opinion testimony by experts “If scientific, technical or other specialized

knowledge will assist the trier of fact to understand the evidence or to determine a fact at issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.”

Admissibility: A Moving Target

Daubert v. Merrell Dow Pharmaceuticals (1993) When expert evidence based on “scientific

knowledge” is offered at trial, the judge acts as gatekeeper to determine if the evidence is “reliable”

Four suggested factors in determining reliability

Testable using the scientific method Peer reviewed Error rates Acceptability to the scientific community

Trial judge given lots of flexibility Muddy waters—what is scientific knowledge?

What about other types of experts?

Admissibility: A Moving Target

Why Daubert won on appeal When Congress passed Rule 702 it

ignored the Frye general acceptability criterion

Frye was no longer “good law”--

Admissibility: A Moving Target

Kumho Tire Co v. Carmichael (1999) Daubert factors are extended to non-

scientist expert witnesses. Daubert factors are not the only ones

that can be considered Trial judge now has enormous flexibility

And it’s not settled yet…..

Daubert and Kumho apply to federal cases only

18 State Courts have adopted Daubert standards

Other State Courts have rejected Daubert and still use a modified Frye standard

Miranda vs. Arizona (1966)

Before questioning by the police, suspects must be informed that they have: The right to remain silent The right to consult an

attorney If indigent an attorney will

be provided for them Anything they say may be

used against them in court Arizona Department of Library Archives and Public Records)

Results of Miranda

Confessions are less likely to hold up in court since the burden of proof of Miranda statement lies on police

Police and prosecutors rely more independent (scientific) evidence to prove guilt

Dickerson

Dickerson vs US (2000) Congress passed law in 1968 saying

voluntary confessions are exempt from Miranda

Supreme Court overrules Congress in 2000

Congress can’t overrule the Supreme Court on constitutionally guaranteed rights except by the amendment process

What’s driving the growth of FS?

Miranda decision Fewer confessions

Increase in drug seizures and arrests More testing

DNA profiling More testing with sophisticated

equipment Other new technologies

Crime Wave or Better Enforcement?

Federal Drug Seizures

Coast Guard Drug Seizures

Arrests by Drug Type

Average % THC in Marijuana Seizures

http://www.usdoj.gov/ndic/pubs11/18862/images/fig1.gif

Recent seizures in Atlanta had plants with 18% THC content.

The Economics of Drugs According to the United Nations Office on Drugs

and Crime, "[T]he value of the global illicit drug market for the year 2003 was estimated at US$13 bn [billion] at the production level, at $94 bn at the wholesale level (taking seizures into account), and at US$322bn based on retail prices and taking seizures and other losses into account."

This is larger than the total economies of 88% of the countries in the world!

Source: United Nations Office on Drugs and Crime (UNODC), World Drug Report 2005 (Vienna, Austria: UNODC, June 2005), p. 127.

And Now for Some Expert Testimony

My Cousin Vinny

http://myafn.dodmedia.osd.mil/img/tv/criticschoice/cousinvin.jpg

A Big Driver in the Plot

Could Mona Lisa testify?

The Forensic All Stars

Mathieu Orfila (1787-1853)Father of toxicology

Alphonse Bertillon (1853-1914)First system of personal identification

Francis Galton (1822-1911)Classification of fingerprints

Dr. Leon Lattes (1887-1954)Determination of blood groupings from

dried blood stains

The Forensic All Stars

Calvin Goddard (1891-1955)Father of ballisticsUse of comparison microscope

Albert S. Osborn (1858-1946)Fundamental principles of document

examinationWalter C. McCrone (1916-2002)

Application of microscopy to analytic problems

The Forensic All Stars

Hans Gross (1847-1915)First text detailing application of

science to criminal investigation

Edmond Locard (1877-1966)Locard’s Exchange Principle

There is an exchange of materials whenever two objects come in contact

Activity Time!

Assign each of the items in your evidence list to the proper department in the crime lab

Feel free to add more types of evidence

Populate your crime lab with your favorite TV characters

Analytic vs. Forensic ChemistryDifferences

Analytic Known source Good idea of what the composition is

likely to be Used for quality control Well defined samples and controls

Forensic Need to determine source Little knowledge of composition Often complex mixtures so hard to

find appropriate controls