Applied Research and Development of a Three-dimensional Topography System for Firearm Identification using GelSight

The proposed work will investigate and develop a novel, accurate, and low-cost system for structural 3D imaging and comparison of cartridge cases and will demonstrate the system's potential for increasing the quality and reducing the cost of forensic analyses. The proposal directly addresses several aims of the NIJ's Applied Research and Development in Forensic Science for Criminal Justice Purposes program: it increases the quality and efficiency of forensic analysis, it develops new instrumentation systems, and it provides a novel approach to enhancing the analysis and interpretation of forensic data derived from physical evidence. Several recent studies have called for improved imaging technology and matching algorithms to support firearm identification. Our project combines the recently developed GelSight high resolution surface topography imaging system with state-of-the-art algorithms for matching image features. The proposed system has a per-pixel resolution of 0.8 microns. Compared to competing technologies, our GelSight based system is fast, inexpensive, and not sensitive to the optical properties of the material being measured. Two completed cartridge case feasibility studies, described in this proposal, demonstrate extremely promising imaging and matching results. The proposal will be completed by Cadre Research Labs, a scientific computing contract research organization, working in collaboration with GelSight Inc, a company formed by the MIT researchers who developed the GelSight surface topography imaging technology. The two companies will collaborate closely with Todd Weller, a firearms identification specialist and Criminalist in the Oakland Police Department. Todd has over 12 years of forensic experience and graduated from the National Firearms Examiner Academy (NFEA). Successful completion of the proposed work will result in the creation of several prototype imaging and comparison systems (Aims 1 and 2), several moderate scale cartridge case comparison studies (Aims 3A and 4), the development and evaluation of advanced feature matching algorithms (Aim 4), and initial field testing at the Oakland, California Police Department (Aim 3B). The completion of these aims will provide valuable information on hardware and software design modifications for maximizing usability and accuracy. The resulting model will have a solid statistical foundation and will allow us to compute the statistical significance of each match. In future work, the proposed framework can be extended to a range of other tool mark comparisons (e.g., bullets and marks of forced entry). Overall, this work will develop analytic techniques, grounded in mathematical science and able to provide accurate quantitative sample comparison and database search. This will benefit law enforcement and their ability to present firearm identification and tool mark evidence in the courtroom. Upon completion of the proposed project we will have created the first deployable version of the GelSight based imaging system and we will begin a larger pilot study at selected state and local forensic labs. ca/ncf