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Warren EM, Sheets HD. Statistical Approaches to Type Determination of the Ejector Marks on Cartridge Cases. J Forensic Sci. 2017;63(2):431-439doi: 10.1111/1556-4029.13529.
Warren, E. M., & Sheets, H. D. (2018). Statistical Approaches to Type Determination of the Ejector Marks on Cartridge Cases. Journal of forensic sciences, 63(2), 431-439. https://doi.org/10.1111/1556-4029.13529
Warren, Eric M, and Sheets, H David. "Statistical Approaches to Type Determination of the Ejector Marks on Cartridge Cases." Journal of forensic sciences vol. 63,2 (2018): 431-439. doi: https://doi.org/10.1111/1556-4029.13529
Warren EM, Sheets HD. Statistical Approaches to Type Determination of the Ejector Marks on Cartridge Cases. J Forensic Sci. 2018 Mar;63(2):431-439. doi: 10.1111/1556-4029.13529. Epub 2017 May 02. PMID: 28464307.
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J Forensic Sci. 2018 Mar;63(2):431-439. doi: 10.1111/1556-4029.13529. Epub 2017 May 02.

Statistical Approaches to Type Determination of the Ejector Marks on Cartridge Cases.

Journal of forensic sciences

Eric M Warren, H David Sheets

Affiliations

  1. Firearm and Toolmark Identification Unit, Tennessee Bureau of Investigation, Nashville, TN, 37216.
  2. Department of Physics, Canisius College, 2001 Main Street, Buffalo, NY, 14208.

PMID: 28464307 DOI: 10.1111/1556-4029.13529

Abstract

While type determination on bullets has been performed for over a century, type determination on cartridge cases is often overlooked. Presented here is an example of type determination of ejector marks on cartridge cases from Glock and Smith & Wesson Sigma series pistols using Naïve Bayes and Random Forest classification methods. The shapes of ejector marks were captured from images of test-fired cartridge cases and subjected to multivariate analysis. Naïve Bayes and Random Forest methods were used to assign the ejector shapes to the correct class of firearm with success rates as high as 98%. This method is easily implemented with equipment already available in crime laboratories and can serve as an investigative lead in the form of a list of firearms that could have fired the evidence. Paired with the FBI's General Rifling Characteristics (GRC) database, this could be an invaluable resource for firearm evidence at crime scenes.

© 2017 American Academy of Forensic Sciences.

Keywords: Glock; Naïve Bayes classification; Smith & Wesson Sigma; ejector marks; forensic science; morphometrics

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