Chemical and morphological investigations of the Ontogenetic effects of Novel Psychoactive Substances on forensically important blowfly species (Diptera: Calliphoridae).

Abstract

Post Mortem Interval (PMI) estimation is a key concern of forensic entomology research. Numerous factors are recognized to affect these calculations, and have shown to potentially introduce error, leading to an incorrect time of death estimation. One such acknowledged factor is the presence of drugs and toxins. A range of Novel Psychoactive Substances (NPS), common adulterants and one illegal drug were tested on two blowfly species, of forensic importance, Calliphora vicina and Lucilia sericata (Diptera: Calliphoridae). An artificial diet was used to enable effective delivery of the substances; the effect on development was studied by observing larval length, weight, instar and time taken to reach pupariation. As a potential alternative for accurate aging, the cuticular hydrocarbon profile was analysed for changes in response to drug presence. Preliminary investigations were also carried out to detect the presence of NPS within larvae, by extraction and derivatisation. The NPS had a profound effect on the development of immature larval samples; rates were mostly accelerated, shown by larval length, weight and an increase in time taken to reach pupariation. A potential PMI overestimation of 48 hours was presented for a number of substances. Paracetamol was the only drug shown to produce developmental delay, up to 48 hours for a higher dose. The effects of drug dosage and potential to use data from chemically similar drugs for PMI estimations are presented; MDA is compared with NPS, 6APB. Noteworthy, the cuticular hydrocarbon profile showed no major changes in response to the drugs, some minor differences were observed but this was less pronounced than the development data and has lesser effect on PMI estimation. Results encourage the use of cuticular hydrocarbon analysis for accurately aging blowfly, despite showing developmental changes triggered by drug ingestion, which may otherwise cause incorrect PMI estimations.