Micro-computed tomography for gunshot residue detection: A systematic review and meta-analysis of distance-dependent deposition patterns.

Micro-computed tomography (micro-CT) has emerged as a non-destructive technique for three-dimensional visualization of radiodense gunshot residue (GSR), yet its quantitative performance and variability have not been systematically evaluated. This systematic review and meta-analysis synthesized experimental evidence on micro-CT-based detection of inorganic GSR. Following PRISMA guidelines, six studies were included, of which four provided data for quantitative synthesis. Random-effects meta-analyses showed a progressive decline in detectable residue with increasing shooting distance, with pooled detection rates of 0.133% at 5 cm and 0.019% at 30 cm, accompanied by extreme between-study heterogeneity (I² > 99%). Quadratic mixed-effects meta-regression identified a significant nonlinear association between distance and detection, with a predicted maximum at approximately 17.79 cm, although distance explained only a small proportion of variability. Exploratory Gaussian modeling revealed marked substrate-dependent differences in detection profiles. Overall, micro-CT consistently enabled non-destructive three-dimensional localization and volumetric assessment of radiodense particles but showed limited capacity for standalone inferential applications, particularly shooting-distance estimation. These findings support its role as a complementary screening and mapping tool within forensic ballistic investigations while highlighting the need for standardized protocols and confirmatory compositional analyses. Clinical trial number: not applicable.