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Establishing likelihood ratios for patterned garment comparisons from seam measurement data.
D B Johnson1, Victor E Perlin, Mitchell M Rohde
1Quantum Signal LLC, 200 N. Ann Arbor St., Saline, MI 48176, USA.
Journal of Forensic Sciences
|April 5, 2013
Summary
This study introduces a quantitative method to objectively measure confidence in identifying patterned garments from crime scene images. The new approach provides a reliable lower bound for likelihood ratios (LRs) in forensic garment comparisons.
Area of Science:
- Forensic Science
- Pattern Evidence Analysis
- Statistical Modeling
Background:
- Objective confidence measures are lacking for identifications from surveillance imagery.
- Garment comparison evidence from crime scenes requires robust quantitative assessment.
- Existing methods struggle to provide reliable confidence levels for visual identifications.
Purpose of the Study:
- To develop a quantitative method for establishing a conservative lower bound on the likelihood ratio (LR) for patterned garment identifications.
- To address the deficiency in objective confidence measures for forensic identifications based on surveillance imagery.
- To provide a statistically sound framework for evaluating garment comparison evidence.
Main Methods:
- Statistical analysis of pattern offset measurements from comparable garments.
- Development of a quantitative framework for likelihood ratio (LR) estimation.
- Validation through a large-scale empirical study with simulated and human comparisons.
Main Results:
- The developed method established conservative lower bounds on LRs for patterned garment identifications.
- LR lower bounds ranged from approximately 10-1 to over 400-1 across various garment types and image qualities.
- The statistical model demonstrated reliability in both simulated and real-world comparison scenarios.
Conclusions:
- The quantitative method provides an objective measure of confidence for patterned garment identifications.
- This approach enhances the reliability of forensic analysis for surveillance imagery evidence.
- The study offers a validated statistical framework for likelihood ratio determination in garment comparisons.
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