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Experience Report Regarding the Performance of the IBIS Correlator

NCJ Number
212912
Journal
Journal of Forensic Sciences Volume: 51 Issue: 1 Dated: January 2006 Pages: 24-30
Author(s)
Ruprecht Nennstiel M.Sc.; Joachim Rahm M.Sc.
Date Published
January 2006
Length
7 pages
Annotation
This study evaluated the performance of the IBIS correlator, the standard tool used to compare firearm markings on bullets and fired cartridges, based on four data sources used mainly in the operation of the German Federal Criminal Police Office's (BKA's) central collection of evidence ammunition.
Abstract
The study found that when operating a collection of evidence ammunition with the IBIS electronic comparison system, a success rate of 75-95 percent was achieved in comparing cartridge cases, and a success rate of 50-75 percent was achieved for bullet comparison under certain conditions. Consideration of up to 5 or 10 elements of the "hit list" is sufficient. Evaluations of more elements does not improve the success rate. Only ammunition with marks suitable for comparison should be tested, and the complete set of mark types should be combined in the comparison. The size of the database of a caliber group should be kept as small as possible by sorting out evidence ammunition after a suitable period of time. Multiple ammunition specimens of the same test firearm should be used in the electronic comparison. Two or three specimens of the same unrecovered firearm should be included in open-case databases. The following data sources were applied in this study: IBIS test, retrograde checking of known crime links, checking of evidence ammunition from the same firearm, and evaluation of "warn hits" (evidence ammunition already available in the database). In discussing study materials and methods, this paper addresses some characteristics of the BKA's open case file database, the parameter of quality of marks, the database size, the number of available signatures from the same source, and the inspected "hit list" position. 9 tables, 7 figures, and 20 references

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