cedartech presentation

7/31/2019 CedarTech Presentation

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CEDAR-FOX

A Computational Tool for QuestionedHandwriting Examination


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Computational Forensics

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

Forensic Sciences

1. Daubert Ruling2. High Standards established by DNA

3. Computers1. Low Cost

2. Advances in Artificial Intelligence/Pattern Recognition4. Improved Statistical Methods for Evidence

E.g., Aitken and Taroni, Statistics and the Evaluation ofEvidence for Forensic Scientists, Wiley, 2004


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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


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CEDAR Research on Handwriting QDE

Quantifying discriminatory power of handwriting- Testing on national database, twins data

Feedback from QDEs in developing

computational tools- Workshops at ASQDE- JtMtg of MAFS, CAFS

- SWAFDE

Developing Statistical Evidence Theory


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CEDAR-FOX Software System

Principal Functions

Writer Verification/Identification

Document Properties

Signature Verification Document Search


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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


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Writer Verification

Known

Questioned


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Sample Preparation: Rule Line RemovalOriginal Ruled Text

User Control

Removed Lines


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Associating Truth with Word Images

Image

Truth/Transcript

TranscriptMap


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Transcript Mapping


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Extracted Characters (Letters)


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Features Extracted


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Distance and LLR Value

Distance = 0.35

LLR = -0.26Distance= 0.16

LLR = 1.49

Distance = 0.43

LLR = -0.97


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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

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Distance

Probabilitydensity

Same writer

Different writer

0 5 10 15 20 25 30 35 400

20

40

60

80

100

120

Count

Same writer

0 5 10 15 20 25 30 35 400

50

100

150

Distance

Count

Different writer

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

0.5

1

1.5

2 x 10

4

Count

Distance

Same writer

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

0.5

1

1.5

2x 10

4

Distance

Count

Different writer

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

1

2

3

4

5

6

Distance

Probabilitydensity

Same writer

Different writer

Macrofeature: SlantMicrofeature: Letter e

Same

Writer

Different

Writer


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Comparison of Words

Distance = 0.3702

LLR = -0.35

Distance = 0.2022

LLR = 4.44


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Word Shape Comparison


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Bigram Shapes

Distance = 0.1996

LLR = 4.35

Distance = 0.3735

LLR = -0.47


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th combination and similarity score

Comparing Letter Pairs


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Macro Features


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Macro and Micro Feature Scores

PictorialAttribute

Scores

(Macro)

Letter

Formation

Scores

(Micro)


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Results of Verification

Feature Comparison

Table

Strength of Evidence


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Strength of Evidence Computation

Based on similarities ina representativedatabase of 1,500writers providing 3

pages of writing each

Probability distributions

of similarities modeledby Gamma andGaussian distributions


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Similar Writing of Twins

LLR = 7.15


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Ranked Document List

Writer Identification


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Word Recognition

Lexicon Selection


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Word Comparison

And Similarity Score

Word Similarities


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Document Properties


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Document Line Structure

Document Properties


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User selects

Character to be displayed

Comparing Letter Formations


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Contour Display


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Query Image

Searching Documents by Word Image


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Searching Documents by Text Query


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

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

Search Modalities


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Genuine Set Scores for

Questioned

Signatures

Signature Matching


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Available

In Help

Menu

Organized by Topics

Hierarchically

User Manual


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Tool Bar Icons


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CEDAR-FOX is a system for assisting theQDE in dealing with handwriting

Has automated tools for writer/signature

verification/identification

Has tools for case-work display

Computes strength of evidence

Summary


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Due to many functions in CEDAR-FOX it isnecessary to gain familiarity with its use

No formal training program set up yet

Competency Training


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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


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

Eraser Tool

Database Interfaces MySQL

Upgrades to CEDAR-FOX


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Improved Statistical Model Current statistical model in system uses

independence assumption

Performance is not high as with better theoreticalmodels, e.g., neural networks

Plan to incorporate a compromise model e.g.,

pairwise independence

Upgrades to Software: Future Releases


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Future Releases: Line SegmentationImprovements


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