A study on the measurement of GSR with bloodstains by ICP-MS.

Abstract

In forensic laboratories, analytical investigations of gunshot residues (GSRs) are usually conducted by scanning electron microscopy (SEM) in combination with energy dispersive X-ray microanalysis. If GSRs are covered with bloodstains, SEM cannot detect them. In this study, an inductively coupled plasma mass spectrometry method is proposed to solve this problem. Results show that bloodstains did not interfere with GSRs and low-level elements are detected. Qualitative and quantitative analyses of Sn, Sb, Ba, and Pb elements in GSRs are also carried out. Different pretreatment methods are adopted according to the characteristics of different samples. Our investigations suggest that the proposed method has the advantages of low detection limit and high sensitivity and it can be very important in expert testimony.

Key points: GSRs with bloodstains could be successfully detected via ICP-MS and bloodstains did not interfere in GSRs analysis.The best pretreatment method for incident bullet holes with bloodstains was microwave digestion.The best pretreatment method for the region around the bullet hole and the shooter's hand with bloodstains was ultrasonic vibration.For the same shooting distance, GSRs collected from the cloth and the shooter's hand with type 95-1 rifle were higher than that of type 92 pistol.