CEDAR-FOXA Computational Tool for Questioned

Handwriting Examination

Computational Forensics

• Forensic domains involving pattern matching• Motivated by Importance of Quantitative methods in the

Forensic Sciences

1. Daubert Ruling2. High Standards established by DNA3. Computers

1. Low Cost2. Advances in Artificial Intelligence/Pattern Recognition

4. Improved Statistical Methods for EvidenceE.g., Aitken and Taroni, Statistics and the Evaluation of Evidence for Forensic Scientists, Wiley, 2004

• Bureau of Justice Statistics (2002)- Among 50 largest publicly funded crime labs

* 57% perform QD function* 5,231 cases requested* 1,079 backlogged at year end

• Significantly larger case load internationally

• Handwriting is common in QD case work

QDE

CEDAR Research on Handwriting QDE• Quantifying discriminatory power of handwriting

- Testing on national database, twins data

• Feedback from QDE’s in developing computational tools- Workshops at ASQDE- JtMtg of MAFS, CAFS- SWAFDE

• Developing Statistical Evidence Theory

CEDAR-FOX Software SystemPrincipal Functions

• Writer Verification/Identification• Document Properties• Signature Verification• Document Search

Computer System Requirements• Processor

– Pentium class processor– P4 or higher recommended

• Operating Systems– Windows NT, 2000, XP, Vista

• Random Access Memory– 256MB on XP and earlier– 512MB on Vista

• Secondary Storage– 30MB available disk space

Writer Verification

Known

Questioned

Sample Preparation: Rule Line RemovalOriginal Ruled Text

User Control

Removed Lines

Associating Truth with Word Images

Image

Truth/Transcript

TranscriptMap

Transcript Mapping

Extracted Characters (Letters)

Features Extracted

Distance and LLR Value

Distance = 0.35LLR = -0.26

Distance= 0.16LLR = 1.49

Distance = 0.43LLR = -0.97

Histograms and PDFs of Distances

0 5 10 15 20 25 30 35 400

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

Distance

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Same writerDifferent writer

0 5 10 15 20 25 30 35 400

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Same writer

0 5 10 15 20 25 30 35 400

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Distance

Cou

nt

Different writer

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

0.5

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2x 10

4

Cou

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Distance

Same writer

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

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Distance

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Same writerDifferent writer

Macrofeature: Slant Microfeature: Letter “e”

SameWriter

DifferentWriter

Comparison of Words

Distance = 0.3702LLR = -0.35

Distance = 0.2022LLR = 4.44

Word Shape Comparison

Bigram Shapes

Distance = 0.1996LLR = 4.35

Distance = 0.3735LLR = -0.47

“th” combination and similarity score

Comparing Letter Pairs

Macro Features

Macro and Micro Feature Scores

Pictorial Attribute Scores (Macro)

LetterFormationScores (Micro)

Results of VerificationFeature Comparison Table

Strength of Evidence

Strength of Evidence Computation

• Based on similarities in a representative database of 1,500 writers providing 3 pages of writing each

• Probability distributions of similarities modeled by Gamma and Gaussian distributions

Similar Writing of Twins

LLR = 7.15

Dissimilar Writing of Twins

LLR = -98.36

Ranked Document List

Writer Identification

Word Recognition

Lexicon Selection

Word ComparisonAnd Similarity Score

Word Similarities

Document Properties

Document Line Structure

Document Properties

User selectsCharacter to be displayed

Comparing Letter Formations

Contour Display

Query Image

Searching Documents by Word Image

Searching Documents by Text Query

Retrieval: Word Images Retrieval: Words (Text)Retrieval: Word Images

Query: Text Word Query: Word Image Query: Word Image

Search Modalities

Genuine Set Scores forQuestionedSignatures

Signature Matching

AvailableIn HelpMenu

Organized by TopicsHierarchically

User Manual

Tool Bar Icons

• CEDAR-FOX is a system for assisting the QDE in dealing with handwriting

• Has automated tools for writer/signature verification/identification

• Has tools for case-work display• Computes strength of evidence

Summary

• Current system does not replace human examiner– It is a tool that can assist the examiner by

providing quantitative measures• Relationship to Frye, Daubert, Kumho

– Method produces reproducible results• Under same inputs

– Error rates can be established using system on large number of cases

Case Work Application

• Due to many functions in CEDAR-FOX it is necessary to gain familiarity with its use

• No formal training program set up yet

Competency Training

• Has been tested by several agencies:– Canada Border Agency– FBI with results presented at ASQDE-Montreal– USSS internal testing– Trial versions with several QDEs

• Further feedback solicited

QD Community Acceptance

• To be included in CEDAR-FOX version 1.2– Additional Tools for Image Manipulation

• Eraser Tool– Database Interfaces

• MySQL

Upgrades to CEDAR-FOX

• Improved Statistical Model– Current statistical model in system uses

independence assumption– Performance is not high as with better theoretical

models, e.g., neural networks– Plan to incorporate a compromise model e.g.,

pairwise independence

Upgrades to Software: Future Releases

Future Releases: Line Segmentation Improvements

Thank You