Proposed Congruent Matching Cells (CMC) Method for Ballistic Identifications and Evidence Searches*
The "correlation cells" and three-dimensional (3D) topography measurements have been proposed for establishment of the "NIST Ballistics Identification System (NBIS)" [1, 2]. Based on the concept of correlation cells, a "Contiguous Matching Cells (CMC)" criterion is proposed for ballistics identifications using three characteristic parameters of the paired correlation cells: cross correlation function maximum CCFmax, spatial registration position in x-y, and registration angle θ. The proposed CMC criterion can be used for correlations of both geometrical topographies and optical intensity images. It can cover ballistics identifications of all case scenarios of fired bullets and cartridge cases, including damaged bullets and toolmarks. The CMC parameters and algorithms are in the public domain and subject to open tests. A measurement uncertainty and error rate reporting procedure will be developed that can greatly add to the scientific support for the firearm and toolmark identification specialty, and give confidence to the trier of fact in court proceedings. Based on the proposed CMC, a "National Ballistics Evidence Search Engine (NBESE)" is proposed using three search parameters for fast and accurate ballistics evidence searches with national databases.