Kristopher D Wisniewski, Jamie K Pringle, Vivienne G Heaton, Andrew James Mitten

Thermal imaging is commonly used by forensic search investigators to locate missing persons, but there is little research on it’s actual effectiveness to detect individuals after death. This paper aims to answer fundamental questions on how long thermal imaging is effective to detect a body lying on the surface and when is the optimal time in a day to survey.
A simulated murder victim, using a freshly dispatched pig (Sus scrofa) carcass, was left on the soil surface of a test site and imaged three times a day over a 61-day study period. Images were quantitatively analysed to determine what the relative thermal response the cadaver had with respect to background values, with results corrected for daily temperature (ADD) and decomposition rate (TBS scores).
Results evidenced the surface cadaver could be detectable throughout the 61 day study period, but there were differences depending on when the survey was conducted during the day. Morning surveys were found to be optimal up to 10 days PMI (0-90 ADD), evening/dusk surveys optimal from 10 to 40 days PMI (90-400 ADD), midday surveys optimal from 40 to 50 days PMI (400-530 ADD) and then evening surveys to the end of the 61-day (400-680 ADD) study period.
Implications suggest that thermal imaging is recommended to detect missing persons even after death and surveys should be undertaken at specific time periods during the day to improve search detection success if PMI can be estimated.