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Detection of Male Human DNA from Whole Lucilia sericata (Meigen) (Diptera:Calliphoridae) Larvae using the Quantifiler®Trio DNA Quantification Kit

Nutton, Laura (2017) Detection of Male Human DNA from Whole Lucilia sericata (Meigen) (Diptera:Calliphoridae) Larvae using the Quantifiler®Trio DNA Quantification Kit. Masters by Coursework thesis, Murdoch University.

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The practice of DNA profiling in forensics is a routinely performed technique, and is accepted as a scientifically rigorous process with known and understood limitations. The recovery of offender DNA in rape homicide can be complicated; it may be hindered by environmental factors, as well as the naturally acidic environment in the female vaginal tract 1, 2. In the cases of sodomy, the presence of Enterobacter species may compromise or degrade seminal fluid, compromising the quality of the molecular evidentiary value 3. Time is a critical factor in the recovery of offender DNA, and its persistence in cases of heavy decomposition appears to be unsatisfactorily understood from the existing research. The sequential decomposition of biological remains, such as human cadavers, over time is termed taphonomy 4, 5. The observation of the factors affecting decomposition have been, and continues to be, studied widely throughout the field of forensics. The process is predominantly affected by the autolytic processes in the body, and the bacterial digestion of the body, termed putrefaction 4. Both factors can affect the survival of semen and the integrity of molecular biological evidence in a corpse. Traditional methods of semen recovery in sexual assault cases include oral, genital and rectal swabs 3, which in cases of heavy decomposition or insect predation could reduce the genital or rectal tissue architecture for swabbing 6.

The field of entomology is intimately linked to the subject of forensic biology, with the colonisation of cadavers being one of the primary external contributors to decomposition of remains 7. Forensic entomology can inform investigators with regards to an ever-increasing number of evidential aspects; these can include matters such as providing an estimation of the Post Mortem Interval (PMI), an application that is supported by a substantial foundation of research 7-12. There is a strictly sequential nature of many insect species life cycles; additionally, the environmental distributions of different entomology assemblages are well defined.

As a consequence of this pattern of succession the movement of remains, such as occurs in cases of body dumping, can disrupt these cycles or modify the cadaver assemblages and therefore inform the movement of remains 7. As a keystone evidentiary discipline in death and homicide investigation, there is substantial underpinning research supporting many of the aforementioned applications.

Despite its significance in forensic biology, entomological research to date has far from exhausted the avenues of enquiry; one such avenue is the application of entomology in recovery of offender DNA profiles. A common anatomical feature of necrophagous fly species larvae possess an accessory food storage organ, called a crop, within which active digestion does not take place 4, 13. There is existing research that indicates it is possible to recover a Human DNA profile from tissue ingested by various blowfly species 13-21. However, the existing research efforts lack rigorous underpinning experimental work that would allow legitimate forensic application of the results.

A knowledge void currently exists due to the nature of the previous work comprising predominantly of pilot studies and method development research. It is known that the recovery of human DNA is possible, and STR profiles have been determined in past efforts, although the majority were partial profiles 7, 13, 15, 17, 19. In much of the existing literature many of the experimental parameters were unsatisfactorily controlled or reported.

Item Type: Thesis (Masters by Coursework)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Magni, Paola and Chapman, Brendan
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