Accuracy, Efficacy, and Reproducibility of Muzzle-to-Target Distance Determination using Gunshot Residue

This proposal involves conducting a comprehensive, multiphasic study on the accuracy, efficacy, and reproducibility of muzzle-to-target distance (MTD) determinations using gunshot residue (GSR) by practicing forensic examiners. The study is designed to assist in the standardization of GSR distance determination methodology, by working with the GSR community to collect empirical data to assist in standardization. The study will collect a large dataset of reference samples that will be made publicly available after the study. The proposed work will be conducted by Noblis, a nonprofit research company, with extensive collaboration from the National Institute of Standards and Technology (NIST).

The proposed study includes five phases.

Phase 1, GSR MTD Working Group—In Phase 1 the study team will create the GSR MTD Working Group (GSR-WG), which will be a small volunteer working group of GSR practitioners and researchers. The GSR-WG will be consulted frequently to assist in determining in detail the approaches used throughout the study.

Phase 2, GSR Reference Sample Dataset—In Phase 2 the study team will collect a GSR Reference Sample Dataset, following existing and proposed standards and recommendations to create a large reference dataset of exemplars of known distances collected under controlled conditions. The dataset will be made publicly available after the study.

Phase 3, Black Box Evaluation of GSR MTD Determinations—In Phase 3 the study team will conduct a Black Box Evaluation of GSR MTD Determinations by practicing examiners. The study will evaluate these determinations in terms of accuracy (correctness), efficacy (reporting distances with ranges that are specific or narrow enough to be probative), and reproducibility (inter-examiner consistency).

Phase 4, GSR Degradation Study—In Phase 4 the study team will conduct a limited GSR Degradation Study assessing the degradation of GSR samples over weeks or months under various conditions.

Phase 5, Report of Recommendations—In Phase 5 the study team will work with the GSR-WG to evaluate the results of Phases 2-4 and develop a Report of Recommendations, with particular focus on recommendations and implications regarding existing and proposed standards, standard operating procedures, training, and quality assurance. CA/NCF