A new simulation-based model for calculating post mortem intervals using developmental data for Lucilia sericata (Diptera: Calliphoridae)

Homicide investigations often depend on the determination of a minimum post mortem interval (PMI) by forensic entomologists. The age of the most developed insect larvae (mostly blowfly larvae) gives reasonably reliable information about the minimum time a person has been dead. Methods such as Isomegalen-Diagrams or ADH-calculations have problems in their reliability, so we established in this study a new growth model to calculate the larval age of Lucilia sericata. This is based on the actual non-linear development of the blowfly and is designed to include uncertainties, e.g. for temperature values from the crime scene. We used published data for the development of L. sericata (Meigen 1826) and found that PMI calculations based on mean temperatures differ by up to 65% from PMIs based on the actual temperature. Differences of 2◦C in the estimation of the crime scene temperature result in a deviation in PMI calculation of 15 30 %. We also show that determination of the developmental state affects the accuracy of the PMI estimation by up to 75%.