Prism (II): 127 cooling dummy experiments.

The Prism method for temperature based time since death estimation has been demonstrated as a proof of principle in 2021. Now it was validated experimentally. 10 cooling dummies (physical weights from 5.9 kg to 26.9 kg) were fabricated and fitted with temperature probes. A total of 127 dummy cooling experiments were conducted (total cooling time 2082 h, average cooling time 24.6 h) for both regular and elevated starting temperatures, covering ambient temperatures between - 14.0 °C and + 24.0 °C and for different cooling conditions. Cooling data was recorded, then cropped, smoothed, fed into the Prism workflow, and analyzed using dedicated scripts written in the Python programming language. Calculations did not take any additional information into account. No correction factors were needed. General Prism cooling weight curves were confirmed (false ambient temperature and elevated rectal temperature at the time of death). Sub-zero ambient temperature generated unexpectedly large cooling weights. Time since death estimation errors were - 0.29 h ± 5.24 h (whole course of cooling, all experiments) and were typically smaller in earlier stages of cooling. Prism performed relatively well, where conventional temperature based death time estimation struggles. In the future it may potentially be adapted to known conditions. Our results indicate that Prism's cooling weight might serve as a highly individual, case-based data-driven umbrella parameter, replacing (subjectively) estimated parameters.