Interpretation of GSR evidence at activity level: Feasible or impossible?

Interpretation methods for forensic evidence have been an area of great interest within the forensic community for decades, with a more recent focus on activity level methods of interpretation. The fundamentals of evaluative reporting and research papers addressing frameworks for probabilistic modeling of gunshot residue (GSR) evidence as well as variables influencing GSR interpretation, such as transfer and contamination, are summarized in this review. The implications and challenges associated with the projected shift to non-traditional (NT) ammunition are also explored. This narrative/scoping review aims to provide an overview of the current state of activity level interpretation of GSR evidence and identify priorities for focus in future research. Although of high probative value, activity level interpretation of gunshot residue evidence has been applied to a limited extent in casework due to challenges inherent to this type of evidence and probabilistic modeling. The imminent transition to NT ammunition within the European Union will require a significant reimagination of GSR analysis and interpretation. While much work still needs to be undertaken before activity level interpretation of GSR can be routinely implemented in forensic casework, the groundwork has been laid out in the literature reviewed and this review can serve as a point of reference in establishing a standardized practice.