Modern day law enforcement banks heavily on the use of commercial off-the-shelf (COTS) face recognition systems (FRS) as a tool for biometric evaluation and identification. However, in many real-world scenarios, when the face of an individual is occluded or degraded in some way, commercial recognition systems fail to accept the face for evaluation or simply return unusable matched faces. In these kinds of cases, forensic experts rely on image processing techniques and tools, to make the face fit to be processed by the commercial recognition systems (e.g. use partial face images from another subject to fill in the occluded parts of the face of interest, or have a tight crop around the face). In this study, we evaluate the sensitivity of commercial recognition systems to such forensic techniques. More specifically, we study the change in the rank-1 identification result that is caused by forensic processing of faces-of-interest that are unusable by the commercial recognition systems. Further, forensic processing of such faces is more of an art and it is extremely difficult to process faces consistently such that there is a predictable effect on the rank-n identification result. This study is meant to serve as an evaluation of the effect of a few forensic techniques intended to allow commercial recognition systems to process and match face images that were otherwise unusable. Our results indicate that COTS FRS can be sensitive to the subjectivity in facial part swapping and cropping, resulting in inconsistencies in the identification rankings and similarity scores.
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