Evaluating firearm examiner conclusion variability using cartridge case reproductions

Area of Science:

• Forensic Science
• Firearms Examination
• Pattern Comparison

Background:

• Forensic pattern comparison disciplines (fingerprints, footwear, firearms) face criticism for subjectivity.
• Examiner conclusions rely heavily on training and experience, necessitating objective accuracy assessments.
• Variability in firearm test sets can complicate accuracy comparisons between examiners.

Purpose of the Study:

• To assess the accuracy of firearm examiners in cartridge case comparisons.
• To evaluate the utility of a standardized comparison method (double-casting) for black box studies.
• To explore the role of automated comparisons in enhancing examiner reliability.

Main Methods:

• Developed plastic cartridge case reproductions using a double-casting technique.
• Provided double-casts from 21 test sets to firearm examiners for comparison tasks.
• Conducted automated comparisons of cartridge cases alongside human examiner analysis.

Main Results:

• Significant differences were observed in examiner conclusions when analyzing identical evidence.
• The double-casting method ensured consistent detail for all participants.
• Automated comparison metrics demonstrated potential as a quality control tool.

Conclusions:

• Human examiners exhibit variability in interpreting firearm evidence, highlighting the need for objective methods.
• Standardized materials like double-casts are crucial for reliable black box studies in pattern comparison.
• Automated comparisons can serve as a valuable adjunct to human analysis, improving error detection and conclusion strength.