title: Evaluation of GLOCK 9 mm Firing Pin Aperture Shear Mark Individuality Based On 1,632 Different Pistols by Traditional Pattern Matching and IBIS Pattern Recognition.
abstract: Over a period of 21 years, a number of fired GLOCK cartridge cases have been evaluated. A total of 1632 GLOCK firearms were used to generate a sample of the same size. Our research hypothesis was that no cartridge cases fired from different 9-mm semiautomatic GLOCK pistols would be mistaken as coming from the same gun. Using optical comparison microscopy, two separate experiments were carried out to test this hypothesis. A subsample of 617 test-fired cases were subjected to algorithmic comparison by the Integrated Ballistics Identification System (IBIS). The second experiment subjected the full set of 1632 cases to manual comparisons using traditional pattern matching. None of the cartridge cases were "matched" by either of these two experiments. Using these empirical findings, an established Bayesian probability model was used to estimate the chance that a 9-mm cartridge case, fired from a GLOCK, could be mistaken as coming from the same firearm when in fact it did not (i.e., the random match probability).
authors.affiliation: International Forensic Science Laboratory & Training Centre, 410 Crosby Drive, Indianapolis, IN, 46227.
authors.forename: James E
authors.initials: JE
authors.lastname: Hamby
authors.affiliation: Wyoming State Crime Laboratory, 208 S College Drive, Cheyenne, WY, 82007.
authors.forename: Stephen
authors.initials: S
authors.lastname: Norris
authors.affiliation: Department of Sciences, John Jay College of Criminal Justice, City University of New York, 524 West 59th Street, New York, NY, 10019.|Faculty of Chemistry and Faculty of Criminal Justice, Graduate Center, City University of New York, 365 5th Avenue, New York, NY, 10016.
authors.forename: Nicholas D K
authors.initials: ND
authors.lastname: Petraco
keywords: Daubert; Glock; IBIS; false match rate; firearms identification; fired cartridge cases; firing pin aperture shear marks; forensic science; legal challenges; microscopic examination; pattern matching; random match probability