Factors affecting accessibility to blowflies of bodies disposed in suitcases

Abstract

Criminals have been known to dispose of bodies in zipped suitcases in an attempt to conceal murder. In order to investigate the forensic implications of this mode of disposal on calculating time of death, it is necessary to study the accessibility of bodies in suitcases to blowflies (Diptera: Calliphoridae) and the possibility of oviposition and infestation under these circumstances. An experimental apparatus was designed that incorporated different zips (toothed and coil) of various gauges (4-6 mm) above a chicken liver bait. Gravid Calliphora vomitoria and Calliphora vicina females were attracted to and oviposited on and through these zips, both under laboratory and field conditions. Egg laying was significantly more frequent and with greater numbers of eggs when zips were in contact with the bait than when they were placed approximately 6cm above the bait. In the absence of bait, adult females could be stimulated to lay eggs on moistened zips, although the presence of blood accelerated egg laying compared to water alone. No eggs were laid on dry zips in the absence of bait. Of the first instar larvae tested, 89% were able to colonise the bait below the zips by passing through gaps between the teeth. Preliminary field studies using suitcases baited with a pig's head indicated that there was a delay of 1-3 days in oviposition when compared to laboratory conditions. This information has practical value in explaining the presence of larvae on enclosed bodies in suitcases and will help forensic entomologists estimate a more accurate minimum time since death.

Keywords: Accessibility; Blowflies; Forensic entomology; Oviposition; Suitcases; Zips.