An Investigation of a Nondestructive Sampling Method for Determination of Minimum Post-mortem Interval (Minpmi) at Different Temperatures Using Dipteran Larvae.

The determination of the precise identification of forensically important Dipteran species are paramount to the establishment of minimum Post-Mortem Interval (minPMI). Insect specimens collected from a crime scene can be at multiple instars of their life cycle and due to the complexity of identification keys are difficult to identify at the early larval stages. This leads to larvae being predominantly reared to adult stages for their identification, which can be a time-consuming process. Which can be increasingly problematic if the specimens are in limited numbers.

This paper investigates the use of a non-destructive methodology to analyse the cuticular hydrocarbons (CHC) of forensically important flies, the final species focussed on being the Dipteran species in the UK, Calliphora vicina and Lucilia sericata. The non-destructive methodology was first established to determine whether the use would be comparable to current destructive methods used in CHC analysis, and whether the storage or collection method for the specimens affected the methods outcome. The second aim was to discover whether the non-destructive method could distinguish between the CHC profiles of the two fly species and in recognising these variations form an identification. Once distinctions between the species were made, could the method detect temperature changes to the profiles.
Using the non-destructive silica rub method 86,500 samples, were measured, sampled and analysed through oviposition to pupation, by gas chromatography – mass spectrometry (GC-MS). The observed results demonstrate that the individual species can be differentiated and that the temperature variables can also be detected within the species profiles. The capabilities for this technique to be used for identification is significant and shows great potential for developing for use at crime scenes. This technique also shows sizeable capacity for use within the agricultural entomology discipline, with the ability to utilise the low-cost nonskilled sampling methodology out in the field.