Blowfly, Chrysomya megacephala as an alternative specimen in determination of gunshot residue

Abstract

Forensic investigation usually deals with cases involving firearms. Deposition produced on hands and clothes after firearm shooting known as gunshot residue (GSR) is the primary marker, besides the presence of bullet and bullet wound, to prove that a suspect has fired a gun. This study was done to investigate the effects of GSR on development rate of Chrysomya megacephala and to apply the use of C. megacephala larvae in detection of GSR. About 100 larvae, respectively were exposed to two pieces of beef meat, one as control without GSR and another meat with GSR. Development rate of C. megacephala was monitored from larvae weight and length, survival rate and duration of development in each stage of life cycle. Post feeding larvae were used to examine accumulation of GSR. Presence of GSR was confirmed with the content of Plumbum (Pb) and Barium (Ba) as markers for GSR. Larvae from both meat, underwent acid digestion process for isolation of Pb and Ba, and quantitatively analyzed using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). It was found that the presence of GSR depressed the development rates and slowed down the total duration of life cycle approximately up to 12 hours in which larvae contained GSR required 242 hours to complete their development cycle from first instar to adult, compared to control larvae which only required 230 hours. Both of these elements were able to be detected from larvae of C. megacephala taken from meat containing GSR. Significantly higher concentrations of Ba detected within larvae feeding on meat containing GSR compared with control. In death cases, where dead remains underwent an advance decomposition process, the presence of GSR in the larvae system should be taking into consideration, since it may gives an error in estimation of PMI for up to 12 hours. Larvae of C. megacephala were able to be used as an alternative specimen for GSR detection when bullet could not be found at the crime scene and bullet wound could also be traced from highly decomposed body.