Forensic Footwear Reliability: Part III-Positive Predictive Value, Error Rates, and Inter-Rater Reliability

Area of Science:

• Forensic Science
• Criminalistics
• Pattern Evidence Analysis

Background:

• Forensic footwear examination is crucial for linking suspects to crime scenes.
• Estimating examiner performance and reliability is vital for courtroom admissibility.
• Previous studies have varied in methodology and scope, necessitating further research.

Purpose of the Study:

• To quantify the performance of forensic footwear examiners in the United States.
• To determine error rates, predictive values (PV), and inter-rater reliability (IRR).
• To evaluate the impact of different reporting structures on examiner agreement.

Main Methods:

• Collected data from 70 footwear experts over 19 months, involving 12 comparisons each.
• Analyzed over 1000 examiner attributes, 3500 impression features, and 840 source conclusions.
• Calculated error rates, PVs, and Gwet AC2 agreement coefficients for examiner reproducibility.

Main Results:

• Correct predictive value ranged from 94.5% (exclusions) to 85.0% (identifications).
• False-positive rate was 0.48%, false-negative rate was 15.6%.
• Gwet AC2 agreement coefficients indicated substantial (0.751) to moderate (0.692) agreement between raters.

Conclusions:

• Forensic footwear examination demonstrates acceptable performance metrics and reliability.
• A six-level reporting structure shows higher inter-rater reliability compared to a four-level structure.
• The findings contribute to understanding the scientific validity of footwear evidence analysis.