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Determining the accuracy and errors of estimating a shooter's position based on cartridge case ejection patterns.

Andrew Lo1, Eugene Liscio1

  • 1Forensic Science Program, University of Toronto Mississauga, Canada.

Forensic Science International
|October 22, 2021
PubMed
Summary

Investigating shooter position estimation using ejected cartridge cases, this study developed a method with a reference sample set. The research found that more cartridge cases improve accuracy, with 6 cases yielding an average error of 122 cm.

Keywords:
BulletsCartridge case ejectionCartridge casesCrime scene reconstructionFirearms examinationForensic scienceShooter estimationShooter positionShooting incident reconstruction

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Area of Science:

  • Forensic Science
  • Ballistics
  • Crime Scene Reconstruction

Background:

  • Ejected cartridge cases are crucial for reconstructing shooting incidents.
  • Estimating shooter location and encounter dynamics relies on ejection patterns.
  • Current methods lack blind studies on precision and error rates for shooter position estimation.

Purpose of the Study:

  • To propose and validate a method for approximating shooter position using cartridge case ejection patterns.
  • To quantify the precision and error rates in shooter position estimation.
  • To establish a standardized method for investigators using reference ejection patterns.

Main Methods:

  • Collected a reference sample set of over 312 cartridge cases from controlled firings (same firearm/ammunition).
  • Varied firing positions and heights, using a double-handed grip.
  • Tested the proposed statistical method on blind datasets with 1-6 ejected cartridge cases and known direction of fire.

Main Results:

  • Increasing the number of cartridge cases analyzed reduced estimation errors and standard deviation.
  • With 6 ejected cartridge cases, the average error in estimating the shooter's position was 122 cm.
  • The study demonstrated improved estimation accuracy with a larger sample size.

Conclusions:

  • The developed method offers a more reliable approach to shooter position estimation.
  • The accuracy of estimation is influenced by the number of cartridge cases analyzed.
  • Applicability is contingent on firearm type, ammunition, human factors, and environmental conditions.