NAS-labeled exhibits from a different gun than the reference exhibit did appear in the full comparison reports. In fact, when NAS06 was used in the reference, three NAS exhibits from the other SIG Sauer pistol could be found in the comparison report compared to two sister entries from the same pistol. However, none of these comparisons yielded scores that cracked the top 11 rankings by either mark.

With CoBIS staff, we examined the firearms makes and models for the 16 highest-ranked possible matches, on the breech face and firing pin lists, for each of the NAS-labeled exhibits. A wide variety of 9mm pistols appear throughout the listings, including Smith & Wesson, Beretta, and Taurus arms, with smaller numbers of Kahr, Springfield, and Keltec guns. Other SIG models are not uncommon in the listings, but the highest ranks are not dominated by them. It is of interest that some of the NAS casings do frequently match to casings from two runs of near-consecutive serial numbers and, consequently, near-consecutive CoBIS IDs. These likely correspond to large batch sales, such as police department orders. For instance, for the NAS02 casing, the top 16 ranks by firing pin include four entries from one of these runs, entered in 2003 (two other nonrelated SIG exhibits from 2001 are also highly ranked on firing pin); however, none of these pistols appears in the highest ranked possible matches by breech face.3

Independently, a committee subgroup visited the New York City Police Department forensic laboratory and ran tests on NAS01–NAS04; the Albany test had the effect of seeing how these same-gun casings were handled in an RBID of images from new firearms, while the New York City test contrasted that with performance in a large database of crime scene evidence. The results were very consistent with those reported in Table 8-7, against a crime-evidence database of 12,427 exhibits after demographic filtering.4

Basic IBIS Results, NYSP Exhibits

Our work with the NYSP-labeled exhibits described in Box 8-2 was similar to that done for the NAS-labeled exhibits. “New” exhibits were entered into CoBIS, and then subsequently re-imaged for comparisons.


Another oddity that shows up in the top 16 rankings is that the NAS01 and NAS02 casings, in particular, find three test casings—apparently entered by FTI in setting up and maintaining CoBIS’ IBIS equipment—among the top ranks by breech face. The make and model of these test rounds (which stand out in the listings because they, like the NAS-labeled exhibits, do not use the typical CoBIS naming conventions) are unknown. It should be emphasized, though, that although they appear in the high ranks, the actual scores and visual match on the images are unremarkable.


Specifically, when NAS01 was used as the reference, NAS03 was again excluded by the coarse comparison pass; NAS02 was nearly top-ranked on firing pin (but low-ranked on breech face), and NAS04 ranked 90th on firing pin and 673rd on breech face.

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