This article presents a set of matching experiments conducted using a novel 3D imaging and analysis system for cartridge cases, TopMatch.
The system utilizes the GelSight photometric stereo sensor to measure micron scale surface geometry and a novel feature-based matching algorithm to score the geometric similarity between measured surfaces. The matching algorithm separately considers the impressed breech face impression and the striated aperture shear and then combines their similarity into a single confidence score. The system demonstrates excellent recall rates with no false positives across a set of experiments involving 290 firearms and 700 cartridge cases from 24 firearms manufacturers. This is the first publication describing this new technology and the first round of matching results. Improvements to the imaging and matching algorithms are already underway. (Publisher Abstract)