Estimation of changes in breech face and firing pin marks over consecutive discharges and its impact on 2D correlation systems
Date of Graduation
Eberly College of Arts and Sciences
Forensic and Investigative Science
Jacqueline A Speir
When a firearm is discharged, the individual marks of that firearm's breech face and firing pin are imprinted onto the head of the cartridge case. The pattern of these individual marks is reproducible between test fires; however, over a large number of consecutive test fires, it has been observed that minute changes in these individual marks occur. These changes in individual marks have been shown to not affect an examiner in their ability to find an Identification or an Elimination, however, the effect that these changes have on Integrated Ballistic Identification System (IBISRTM) is largely unknown. If these changes in individual marks negatively affect IBISRTM's performance, the reliability of IBISRTM could be called into question. In order to examine the effect on IBISRTM, 200 consecutive test fires were collected from twenty five SR9 Ruger 9mm handguns for a total of 5000 cartridge cases. The cartridge cases were then entered into IBIS RTM and the full correlation list was recorded for each cartridge case. Evaluation of Receiver Operator Characteristic Curves and Area Under the Curve indicated that the changes in individual marks over a number of consecutive test fires does have a negative effect on IBISRTM's performance. Despite this negative effect, IBISRTM still performs well enough to be effective as a screening tool. Secondary objectives of this research include: evaluate IBISRTM's ability to distinguish between Known Match and Known Non-Match, evaluate IBIS RTM's ability to distinguish between Delta 190 Plus Known Match and Known Non-Match, determine if the changes from consecutive test fires follow a pattern, determine if larger rate of change is present in new firearms, and evaluate IBISRTM's ability to distinguish between Known Non-Match comparison between two Ruger SR9 handguns and Known Non-Match comparisons resulting from non-Ruger SR9 comparisons.
Kirk, Justin, "Estimation of changes in breech face and firing pin marks over consecutive discharges and its impact on 2D correlation systems" (2015). Graduate Theses, Dissertations, and Problem Reports. 5985.