Rough mPMI Estimation in Autopsy-Stage Forensic Entomology: Initial Data on Practical Applicability

Abstract

Minimum postmortem interval (mPMI) estimation in forensic entomology generally requires scene investigation and the acquisition of scene temperature and insect evidence. In practice, however, direct scene access by forensic entomologists is often limited. This study estimated a rough mPMI using only insect specimens, case information, and nearby weather station temperature data available at the autopsy-stage, with all insect specimens collected during autopsy and evaluated its practical applicability. Five indoor unattended death cases autopsied in July and October 2023 were examined. For each case, 30 specimens were selected and identified by morphological examination and COI-based DNA barcoding. Rough mPMI was estimated using published developmental datasets based on the identified species, the most advanced developmental stage, and the mean temperature from the nearby weather station during the 7 days before body discovery. Accuracy was assessed by comparison with the last known record from investigative records. Two to four species were identified per case; Lucilia sericata occurred in all five cases and Phormia regina in four. The relative deviation between rough mPMI and the last known record ranged from 3.9% to 60.7% (13.8–130.2 h), with relatively smaller discrepancies in open or well-ventilated cases. In four cases, P. regina served as a key species for mPMI estimation, highlighting the importance of interpreting primary colonizing species in relation to regional and case-specific conditions. These findings suggest that rough mPMI may provide supplementary temporal information at the autopsy stage when scene access is limited.