Infrared imaging as a non-invasive tool for documenting maggot mass temperatures

Abstract

Forensic entomology relies on the ability to predict the temperatures to which maggots have been exposed, due to the resultant impact on their growth rate. Mercury thermometers and electrical temperature sensors have traditionally been used to record temperatures of maggot masses, cadavers and the surrounding soil and air. However, these techniques are limited to one measurement at a time and thus may not accurately describe the complexities of the thermal environment of the cadaver. Infrared imaging has gained increasing popularity because of its resolution, affordability and portability. Using decomposing pig carcasses, the current study showed that surface temperature measurements recorded using temperature loggers are able to be successfully replicated by taking spot measurements from an infrared image. Additionally, by recording the maximum temperature observed within each infrared image, an accurate proxy was achieved for internal temperatures of a carcass placed outdoors (R2=0.46, p<0.001). By studying a pig in a temperature-controlled room and thus removing external environmental factors, the strength of the relationship between maximum infrared temperature and internal carcass temperatures was increased (R2=0.98, p<0.001). This successful characterisation of maggot mass temperatures within carcasses should encourage the application of infrared imaging in forensic entomology research and casework.