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

TL;DR

This study introduces a novel simulation-based model for estimating post-mortem intervals using non-linear developmental data of Lucilia sericata, accounting for temperature uncertainties to improve forensic accuracy.

Contribution

The paper presents a new growth model that incorporates non-linear development and temperature uncertainties for more reliable PMI estimation in forensic entomology.

Findings

PMI estimates vary significantly with temperature inaccuracies.

The model improves PMI accuracy by considering developmental progress within stages.

Temperature deviations of 2°C can cause 15-30% errors in PMI calculations.

Abstract

Homicide investigations often depend on the determination of a minimum post-mortem interval (PMI$_{min}$) by forensic entomologists. The age of the most developed insect larvae (mostly blow fly larvae) gives reasonably reliable information about the minimum time a person has been dead. Methods such as isomegalen diagrams or ADH calculations can have problems in their reliability, so we established in this study a new growth model to calculate the larval age of \textit{Lucilia sericata} (Meigen 1826). This is based on the actual non-linear development of the blow fly and is designed to include uncertainties, e.g. for temperature values from the crime scene. We used published data for the development of \textit{L. sericata} to estimate non-linear functions describing the temperature dependent behavior of each developmental state. For the new model it is most important to determine the progress within one developmental state as correctly as possible since this affects the accuracy of the PMI estimation by up to 75%. We found that PMI calculations based on one mean temperature value differ by up to 65% from PMIs based on an 12-hourly time temperature profile. Differences of 2\degree C in the estimation of the crime scene temperature result in a deviation in PMI calculation of 15 - 30%.