Forensic analysis of C4 explosive residues on post blast hair samples

Abstract

The occurrence of crimes involving high explosives in Malaysia in recent years has warrant the need for the analysis of high explosives in post blast samples, particularly residues that could be found on hairs of victims. This study reports on the detection of post blast residues of C4 explosives on human head hairs. Natural and dyed human head hairs were selected as hair sample in this research. The identification of human head hair on its medullary index (MI) was conducted by using microscopic examination. All hair samples gave MI values of 0.13 µm to 0.29 µm indicative of human head hairs. Prior to a simulated explosion, a bundle of hair (200 strands) was tightly bound to a metal hook at each point of several pre-determined distances from the blast point. Hair samples containing post blast residues were extracted by ultrasonication using acetonitrile. Two analytes of interest, cyclotrimethylenetrinitramine (RDX) and pentaerythritol tetranitrate (PETN) were successfully separated using gas chromatography with electron capture detector (GC-ECD) on an HP5-MS capillary column. It was found that the amount of explosive residues decreased with increasing distance from the point of blast. At the nearest specified distance of 2.5 m, the amount of PETN residues deposited on hair was much less compared to that of RDX residues