Field validation of blow fly age estimation methods for determining time of placement of human remains in Tennessee,...

Forensic entomology currently represents one of the best approaches for estimating the minimum postmortem interval (PMI_MIN) in medicolegal death investigations given certain parameters and assumptions are met. However, validation of standard estimation methods used in this field are few and far between. Our project aimed to quantify errors associated with four aspects of a typical insect age estimation: insect species, development stage, base temperature for calculating accumulated degree hours, and reference dataset. To do this, we collected 725 larval dipteran samples from 79 human donors at the Anthropology Research Facility (ARF) at the University of Tennessee, Knoxville, TN, USA. Standard age estimations were performed with all blow fly larvae to estimate the time of placement of donors and assess accuracy depending on species and larval stage used, base temperature selection, and reference dataset selection. Base temperature selection did not significantly impact estimation accuracy for most (i.e., six out of seven) blow fly species (p > 0.05). However, there was a significant impact of development stage (p < 0.001), reference dataset selected (p < 0.001), and blow fly species used (p < 0.001) on estimation accuracy. Our results underscore the importance of method validation and demonstrate that not all components used for age estimations are equally informative. This dataset currently represents the largest effort to validate blow fly estimation methods using human remains, and one of the only efforts made in forensic entomology to validate developmental datasets to date.