# New alginate-gelatine method for casting of staining inside firearm barrels

## TL;DR

A new method using a gelatine-alginate mixture successfully captures and preserves biological traces inside firearm barrels for forensic analysis.

## Contribution

A novel gelatine-alginate casting method with a central spine enables reliable extraction of biological traces from firearm barrels.

## Key findings

- A 11% gelatine with 1% alginate mixture around a central spine produced consistent castings.
- The method preserved blood and GSR patterns and showed staining gradients in contact shots.
- The technique works for various handgun barrels and allows for targeted molecular genetic analysis.

## Abstract

Contact shots to the head often leave behind biological traces inside firearm barrels, a phenomenon of great forensic interest. Until now, the visualization and preservation of these traces presented a significant challenge, lacking a reliable method. This study addresses this gap by searching for a suitable method to extract the traces within a casting. Using alginate or gelatine as suitable materials, the results were hampered by serious adhesion issues and their extraction out of the firearm barrel was impeded. Finally, the combination of 11% gelatine with 1% alginate, introduced into the barrel around a ‘central spine’, succeeded to consistently produce replicable castings. Experimental contact shots displayed a distinct staining gradient from the muzzle to the rear of the barrel, as revealed through endoscopy and proved in the macroscopic casting. The technique proved effective for various common handgun barrels and successfully preserved blood and gunshot residue (GSR) patterns within the barrel. This method offers the dual benefits of visually mapping staining patterns and securing localized samples for targeted molecular genetic analysis in forensic investigations.