Post-mortem interval estimation based on insect evidence in a quasi-indoor habitat

Abstract

Insects collected on indoor cadavers are frequently used for post-mortem interval (PMI) estimation. Buildings encountered during crime investigations vary according to temperatures inside, the extent of insect access restriction or sanitary conditions. This article reports the PMI oriented analyses of insect evidence sampled from the human cadaver in the atypical indoor habitat. The body was found in the uninhabited house, on the floor covered with rubbish, in the room with no doors and windows. Thermal conditions in the room were less variable than in the local weather station, however still much more variable compared to the typical indoor habitat, indicating the need for retrospective correction of temperature records from the station. Cadaver entomofauna was surprisingly diverse and abundant. We recorded several taxa usually not occurring on indoor cadavers, e.g. immature stages of Necrodes littoralis (Coleoptera: Silphidae) or Stearibia nigriceps (Diptera: Piophilidae). PMI was based on the age and the pre-appearance interval estimated for live puparium of S. nigriceps, giving the total interval of 37 (±7.4) days plus 4-20 days resulting from the absence of first colonizing specimens of the species. This estimate was corroborated with the age estimate for empty puparia of Sarcophaga argyrostoma (Diptera: Sarcophagidae) with traces of Nasonia sp. (Hymenoptera: Pteromalidae) eclosion. Other insects indicated shorter but consistent PMI. Difficulties and limitations of insect-based PMI estimations in unusual indoor habitats are discussed.

Keywords: Forensic entomology; Nasonia; Necrodes; Protophormia; Sarcophaga; Stearibia.