Estimation of temperature-dependent growth profiles for the assessment of time of hatching in forensic entomology

Abstract

Forensic entomology contributes important information to crime scene investigations. In this paper, we propose a method to estimate the hatching time of larvae (or maggots) based on their lengths, the temperature profile at the crime scene and experimental data on larval development. This requires the estimation of a time-dependent growth curve from experiments where larvae have been exposed to a relatively small number of constant temperature profiles. Since the temperature influences the developmental speed, a crucial step is the time alignment of the curves at different temperatures. We propose a model for time varying temperature profiles based on the local growth rate estimated from the experimental data. This allows us to estimate the most likely hatching time for a sample of larvae from the crime scene. Asymptotic properties are provided for the estimators of the growth curves and the hatching time. We explore via simulations the robustness of the method to errors in the estimated temperature profile. We also apply the methodology to data from two criminal cases from the United Kingdom.