Problems in estimating the post-mortem interval (PMI) in death investigations based on insect evidence are well known. For example, insufficient information on fly activity and weather conditions create uncertainties. Many efforts have been made to reduce these problems. Although they have not been entirely successful, insect evidence continues to be used to estimate PMI in two major two ways—through knowledge of rates of insect development or insect succession. The former is more accurate and is the focus of this review. The data can be categorical (the stage of the insect, egg, larval instar, and so forth) or continuous (e.g., larval weight or length). Continuous data can give greater temporal resolution but are open to error introduced by the response of specimens to different rearing and preservation techniques.

This chapter gives an overview and comparison of existing methods to estimate the PMI, namely isomorphen and isomegalan diagrams, thermal summation models, curvilinear models and spectral measurement. It presents some more recent development on the reconstruction of the specimen growth process. These not only provide a lower bound for the PMI, but also offer a diagnostic tool to check that the conditions at which the specimens developed at the crime scene are consistent with the experimental ones.