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

Area of Science:

• Forensic Science
• Ballistics
• Trace Evidence Analysis

Background:

• Contact shots to the head leave biological traces in firearm barrels, crucial for forensic investigations.
• Previous methods for visualizing and preserving these traces were unreliable and challenging.
• A need existed for a robust technique to extract and analyze firearm barrel evidence.

Purpose of the Study:

• To develop and validate a reliable method for casting and preserving biological traces from firearm contact shots.
• To overcome adhesion and extraction issues encountered with previous casting materials.
• To enable detailed analysis of trace evidence for forensic casework.

Main Methods:

• A novel casting technique was developed using a combination of 11% gelatine and 1% alginate.
• A 'central spine' was utilized within the barrel to facilitate consistent casting.
• The method was tested on experimental contact shots in common handgun barrels.
• Endoscopy and macroscopic examination were used to analyze the castings.

Main Results:

• The gelatine-alginate casting method successfully produced replicable results.
• A distinct staining gradient of biological traces was observed within the barrel.
• The technique effectively preserved blood and gunshot residue (GSR) patterns.
• The method demonstrated efficacy across various handgun barrel types.

Conclusions:

• The developed casting technique provides a reliable solution for visualizing and preserving firearm contact shot traces.
• This method allows for both macroscopic pattern mapping and targeted molecular genetic analysis.
• It significantly enhances the ability to collect and analyze critical forensic evidence from firearm barrels.