Examination of forensic entomology evidence using computed tomography scanning: case studies and refinement of techniques for estimating maggot mass volumes in bodies
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A new technique has recently been developed for estimating the volume of maggot masses on deceased persons using post-mortem CT scans. This allows volume to be measured non-invasively and factored into maggot mass temperature calculations for both casework and research. Examination of admission scans also allows exploration of entomological evidence in anatomical areas not usually exposed by autopsy (e.g. nasal cavities and facial sinuses), and before autopsy disrupts the maggot distribution on a body. This paper expands on work already completed by providing the x-ray attenuation coefficient by way of Hounsfield unit (HU) values for various maggot species, maggot masses and human tissue adjacent to masses. Specifically, this study looked at the HU values for four forensically important blowfly larvae: Lucilia cuprina, L. sericata, Calliphora stygia and C. vicina. The Calliphora species had significantly lower HU values than the Lucilia species. This might be explained by histological analysis, which revealed a non-significant trend, suggesting that Calliphora maggots have a higher fat content than the Lucilia maggots. It is apparent that the variation in the x-ray attenuation coefficient usually precludes its use as a tool for delineating the maggot mass from human tissue and that morphology is the dominant method for delineating a mass. This paper also includes three case studies, which reveal different applications for interpreting entomological evidence using post-mortem CT scans.
KeywordsForensic entomology Maggot mass Computed tomography Volume X-ray attenuation coefficient
This project was funded by ARC Linkage Grant LP0883711. We thank the Australian Federal Police and the NSW Police Force for their financial support, and the Victorian Institute of Forensic Medicine, Victoria Police and Forensic Science SA for their in-kind support. We are also grateful to Dr Marijka Batterham (UOW) for her assistance with the statistical analysis of the data.
Ethics approval for the use of de-identified CT scans of deceased was granted by the Ethics Committee of the Victorian Institute of Forensic Medicine.
Conflicts of interest
The authors declare that they have no conflict of interest.
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