Interaction of bullets with intermediate targets: material transfer and damage

Area of Science:

• Forensic Science
• Materials Science
• Ballistics

Background:

• Determining bullet origin and trajectory in complex shooting incidents is challenging.
• Microtraces on bullets are often overlooked but contain vital forensic information.
• Understanding material transfer is key for trajectory reconstruction and legal implications.

Purpose of the Study:

• To investigate microtraces on bullets after perforation and ricochet.
• To analyze material transfer from different target materials onto two bullet types (FMJ and LRN).
• To assess the potential of microtrace analysis for determining impact order and trajectory.

Main Methods:

• Fired 179 bullets (FMJ and LRN) into 5 different target materials (MDF, greenboard, gypsum fibreboard, glass, steel).
• Varied incident angles (90°, 10°, 5°) to simulate perforation and ricochet scenarios.
• Utilized Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM/EDX) to analyze microtraces.

Main Results:

• Traces from target materials were found on bullets in most perforation and ricochet cases.
• Stratification of traces indicated the order of impact, allowing for trajectory reconstruction.
• Softer Lead Round-Nose (LRN) bullets showed greater material transfer than harder Full Metal Jacket (FMJ) bullets.
• Distinct traces were observed on glass during ricochet, and wipe-off from LRN bullets was sometimes visible.

Conclusions:

• Microtrace analysis on spent bullets provides significant forensic evidence for trajectory reconstruction.
• The study demonstrates the feasibility of determining impact sequence through stratified trace analysis.
• SEM/EDX is a valuable tool for identifying and characterizing microtraces in forensic investigations.