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Evaluating firearm examiner conclusion variability using cartridge case reproductions.

Eric F Law1, Keith B Morris1

  • 1Department of Forensic and Investigative Science, West Virginia University, Morgantown, WV, USA.

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|May 31, 2021
PubMed
Summary

Forensic examiners showed variability in conclusions on firearm evidence. Automated comparisons can enhance accuracy and serve as a quality control for pattern comparison disciplines.

Keywords:
black box studybreech facecartridge case variabilitycongruent matching cellsdouble-castingerror ratesfirearm tool markfirearms identification

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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.