An extraction method using whole insect larvae to isolate DNA from a deceased host.

Abstract

The analysis of entomological evidence continues to be a useful method for the identification of human remains from a crime scene, especially when the body is in a state of decomposition. During active decomposition the DNA within the organism may also degrade and could inhibit the ability to develop a genetic profile from traditional samples, such as blood and tissue from the body. Collection of entomological evidence such as larvae that developed on a body can provide a source of DNA to generate a genetic profile from a corpse. Typically DNA profiles obtained from larvae samples involved dissecting and removing crop contents. Dissection and removal of crop contents requires use of precise tools and entomological training, which most forensic laboratories do not have. This research assessed whole larvae DNA extraction, as a means to identify their food source. Two pigs, which were used as human analogs, were deposited in a secluded area and allowed to decompose. Pig #1 was unaltered, while pig #2 was deposited with commercially purchased human semen placed in several locations on the pig, to simulate the events of a sexual assault homicide. In total, forty-eight larvae extracts were analyzed with an Animaltype Pig PCR amplification kit. Four of these larvae extracts produced at least one callable allele at one locus with the Animaltype Pig PCR amplification kit. Fifty samples were amplified using an Applied Biosystems AmpFlSTR?« Y-Filer PCR amplification kit. Seven of these larvae samples produced at least one callable allele at one locus with the Applied Biosystems AmpFlSTR?« Y-Filer PCR amplification kit. Amplification of whole larvae extracts with the Animaltype Pig PCR amplification kit did not provide consistent results, but it did demonstrate the ability to develop a profile by extracting whole larvae. Whole larvae extracted from pig #2 indicated that a possible suspect's genetic profile could be obtained from whole larvae extraction; however, human commercial semen was consumed early in the decomposition of the pig carcass. The results from this research serve as a template for future forensic molecular biology research.