Cuticular hydrocarbons of pupal cases of Chrysomya megacephala (Fabricius) and its possible use for estimating postmortem interval

Abstract

Pupal cases of Chrysomya megacephala are commonly found at death scenes; however, its utilization for forensic investigation remains nascent. Although the use of cuticular hydrocarbons (CHCs) for estimating the age of pupal cases has been reported, they were either laboratory-controlled experiments or in environmental conditions peculiar to Malaysia. Hence, this present research examined the CHCs in the pupal cases of C. megacephala exposed to the natural weathering in Malaysia provides empirical evidence for its age estimation. While confirmation of the identity of CHCs was done using gas chromatography-mass spectrometry, gas chromatography-flame ionization detector was used for quantifying the concentrations. The hexane extract of the pupal cases of C. megacephala contained a mixture of odd-numbered high molecular weight aliphatic (heptacosane (n-C27) and nonacosane (n-C29)), and branched alkanes (tetradecane, 2,6,20-trimethyl- and octadecane, 3-ethyl-5-(2-ethylbutyl)). Significant decrease (p <0.05) in the concentrations of n-C27 and n-C29 was observed, with the pattern being highly correlated (r > -0.926) with that of subsequent weathering intervals. Such findings had enabled formulation of credible mathematical algorithms for relating the concentrations of n-C27 and n-C29 in the pupal cases of C. megacephala versus the natural weathering intervals for its age estimation in Malaysia.