Photo Credit: Getty Images/Rob Ault
Researchers from the University of Western Australia’s Centre for Forensic Science have collaborated with the University of Turin’s Department of Chemistry in Italy to develop a gas chromatography–mass spectrometry (GC–MS) method to analyze levels of methamphetamine (MA) in blowflies (Calliphora vomitoria L.). The method published in the journal Forensic Science International could be performed by forensic scientists collecting evidence related to cause of death in cases of suspected methamphetamine use or overdose.
Blowflies are one of the first insects to colonize decomposing tissue hours after death. Their life-stages are characterized by different body structure and composition, and so can be used as a stopwatch of how long decomposition has been occurring. In cases of suspected toxin exposure where decomposition has progressed, blowflies that have fed on the corpse can be analyzed to detect suspected toxins. Paola Magni, corresponding author of the paper, told The Column: “Several studies have demonstrated that the toxicological analyses of insect material are able to provide a more reliable and sensitive result than from highly decomposed remains (both corpse and carcasses). Many substances (drugs, pesticides, and toxic metals) have been detected in insect tissues, and a relationship between the drug found in the substrate and insects reared on that substrate have been determined.”
Blowfly colonies were reared on beef liver samples spiked with either 5 ng/mg or 10 ng/mg of methamphetamine; concentrations associated with human deaths and sometime with fatal overdose. Larvae and adults were sampled at regular intervals and prepared for analysis by GC–MS. Magni said: “The present research shows the development of a suitable analytical method using GC–MS to detect this drug in larvae, pupae, spent pupae, and adults of C. vomitoria.”
The researchers were able to successfully detect methamphetamine in the blowflies sampled. Furthermore, they observed that methamphetamine ingestion increased the time for development from egg to adult, 60% of larvae died during pupation, and surviving larvae and pupae were larger than controls. Magni told The Column: “The sampling of the flies should be done following the best practices in forensic entomology. For chemical analyses the samples are stored at -20 °C until MA is extracted; for morphological analyses using hot water and ethanol to maintain their structural features. The chemical process of extraction of MA has to be performed carefully because the insect samples are not ‘clean’ and can leave residues that cause problems in the GC–MS instrument.” — B.D
1. P.A. Magni, T. Pacini, M. Pazzi, M. Vincenti, and I.R. Dadour, Forensic Science International 241, 96–101 (2014).