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Fire Cartridge Case Identifications Using Optical Images and Congruent Matching Cells (CMC) Method



D Ott, Jun-Feng Song, Wei Chu, Robert M. Thompson


The Congruent Matching Cells (CMC) method was invented at the National Institute of Standards and Institute (NIST). The CMC method is based on correlation of pairs of small correlation cells instead of correlation on the entire images. Four identification parameters are proposed for uniquely identifying correlated cell pairs originating from the same firearm. The correlation conclusion (matching or non-matching) is determined by the qualified CMC numbers C ≥ 6. This method has already been validated by a set of 780 pair-wised 3D topography images captured on 40 cartridge cases fired from handguns with 10 consecutively manufactured pistol slides. However, most ballistics images stored in current firearm databases are 2D optical intensity format. As a result, reliability of applying the CMC method on 2D optical intensity images is an important issue, and the validation test is highly demanded. In this paper, optical intensity images captured on the same set of 40 cartridge cases are correlated and analyzed. That includes correlations of 63 pairs of matching images and 717 pairs of non-matching images under top ring lighting and 3 o'clock side lighting conditions. Test results do not produce any false identification (false positive) or false exclusion (false negative) result, which strongly support the CMC method and the identification criterion C ≥ 6 for accurate firearm identifications of optical intensity images.
Journal of Research (NIST JRES) - 119.023
Report Number


Ballistics identification, Image processing, Cartridge case, Correlation cells, Congruent Matching Cells (CMC)


Ott, D. , Song, J. , Chu, W. and Thompson, R. (2014), Fire Cartridge Case Identifications Using Optical Images and Congruent Matching Cells (CMC) Method, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed May 18, 2024)


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Created November 5, 2014, Updated November 10, 2018