Forensic Science Institute

Tag: firearms identification

Research: The Empirical Evaluation and Examination of Breechface Markings on Ten Consecutively Manufactured Pistol Slides

Previously published research and case studies exist pertaining to consecutively manufactured tool marks and the individuality of those markings on tools. This study seeked to assess the Association of Firearm and Tool Mark Examiners (AFTE) Theory of Identification and provide additional research into the investigation of characteristics potentially viewed on the breechfaces of pistol slides. The researcher obtained ten consecutively manufactured Ruger LCP .380 Auto slides for examination. The tool marks exhibited on the breechfaces were macroscopically examined, evaluated in terms of potential for the transfer of subclass characteristics, and examined for the presence of individual characteristics. This research indicated whether breechface markings were accorded to their respective slide or if misidentification by examiners was possible. The importance of this study was in validating the AFTE Theory of Identification through generation of a test for AFTE members. This test required examiners to distinguish between subclass and individual characteristics, identify cartridge cases to their respective slide, and determine whether there was potential for misidentification of breechface markings due to subclass carryover. This study might also function as a test for firearm and tool mark examiners to utilize in their laboratories as a training exercise related to consecutively manufactured breechfaces. The research findings might also facilitate the development of error rates pertaining to this study.

Posted on April 16, 2019 by Dr. Mark McCoy

Research: External Validation of Consecutive Matching Striae Technology

Firearm and tool mark identification relies on criteria that have been accepted in the field to assist firearm examiners in determining if a bullet is fired from a particular firearm. In this research, criteria for firearm conclusions were reviewed, in light of current challenges by the scientific and legal community, concerning the reliability of firearm and tool mark identification theories. The aim of the research is to determine the effectiveness of Consecutive Matching Striae (CMS) criteria with respect to two-dimensional and three-dimensional marks viewed on both known and unknown test bullets of different caliber weapons. This research was conducted using .25 Auto, .380 Auto, .38 SPL, 9mm, .40 S&W, .45 Auto, and 7.62×39mm bullets. All data were used to evaluate the validity of CMS for identification purposes by examining groove impressions. The results revealed that current CMS criteria were valid for firearm identification but some known match comparisons were excluded. Therefore, new proposed criteria were demonstrated for assistance of firearm identification.

Posted on April 16, 2019 by Dr. Mark McCoy

Research: Approaching Objectivity in Firearms Identification: Utilizing IBIS BULLETTRACE-3D’s Sensor Capturing Technology

Firearm examiners are often asked 1) can bullets be matched back to cartridge cases? 2) What bullets leave suitable markings? 3) Does an objective approach for interpreting firearm examiner conclusions exist? The inability to objectively answer questions related to linking evidence and source in firearm and tool mark analysis suggests the need for further studies that offer appropriate, reliable conclusions. The purpose of this study was to provide an objective approach for interpreting Firearm examiner conclusions. A fixed-bin analysis consisting of 53 bins in a side-by-side representation was utilized to analyze regions of interest on a single bullet’s bearing surface acquired in 1.6mm (band) increments by the IBIS BULLETTRAX-3D^TM system. Results address concerns that have been outlined by the National Research Council (2009). Major findings in this study indicate the IBIS BULLETTRAX-3D^TM system can assist examiners with better visualization and the ability to provide objective conclusions in bullet comparisons.

Posted on April 16, 2019 by Dr. Mark McCoy

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