CEDARFOX-020907.pdf
- 1. Computational Approaches to Questioned Handwriting Examination Sargur (Hari) Srihari University at Buffalo State University of New York
- 2. Computational Forensics Forensic domains involving pattern matching Motivated by Importance of Quantitative methods in the Forensic Sciences 1. Daubert Ruling 2. High Standards established by DNA 3. Computers 1. Low Cost 2. Advances in Artificial Intelligence/Pattern Recognition 4. Improved Statistical Methods for Evidence E.g., Aitken and Taroni, Statistics and the Evaluation of Evidence for Forensic Scientists, Wiley, 2004
- 3. QDE 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
- 4. CEDAR Research on Handwritten QDE Research on quantifying discriminatory power of handwriting since 1999 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
- 5. CEDARFOX software system Writer Verification/Identification Probability/Strength of Evidence Computation Document Properties Line Structure, Writer Characteristics Signature Verification Document Search System Requirements Pentium class processor (P4 or higher recommended) Windows NT, 2000 or XP 128MB of RAM 30MB available disk space
- 7. Result of Verification Feature Comparison Table Strength of Evidence
- 8. How is Strength of Evidence Computed? Handwriting characteristics are extracted from both K and Q and their similarities compared to the similarities in a representative database Based on a data base of 1,500 writers providing 3 pages of writing each Probability distributions of similarities modeled by Gamma and Gaussian distributions
- 9. What Handwriting Characteristics are Computed? Pictorial Attribute Scores Letter Formation Scores
- 11. Document Properties Document Line Structure
- 14. Comparing Letter Formations User selects Character to be displayed
- 15. Comparing Letter Pairs th combination and similarity score
- 16. Word Similarities Word Comparison And Similarity Score
- 17. Sample Preparation: Rule Line Removal Original Ruled Text User Control Removed Lines
- 18. Signature Matching Genuine Set Scores for Questioned Signatures
- 20. Search Modalities Retrieval: Word Images Retrieval: Words (Text) Retrieval: Word Images Query: Text Word Query: Word Image Query: Word Image
- 21. User Manual Available In Help Menu Organized by Topics Hierarchically
- 22. Summary CEDAR-FOX is a system for QDE with a focus on handwriting Has automated tools for writer/signature verification/identification Has tools for case-work display Computes strength of evidence
- 23. Future Work Better 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
- 24. Future Work: Line Segmentation
- 25. Thank You Further Information: srihari@cedar.buffalo.edu ycshin@cedartech.com