The species and developmental stages of insects and their larvae found in and around a corpse can provide an accurate estimate of when the person died or when the body was left at the spot where it was found. Insect analysis may indicate whether the body was moved from the place of death and the general location where a homicide occurred. Insect species such as the blow fly often lay eggs on a corpse within 10 minutes of death. This article explains how an analysis of the developmental stages of maggots, which are the larvae of flies, can provide an estimate of when death occurred. The article notes that forensic entomology (the study of insects) is an exact science supported by hard data derived from experiments. Some of these experiments are described, notably those conducted with pig carcasses, which decompose in nearly the same ways as a human body. The article advises that it is best to invite a forensic entomologist to examine an undisturbed murder scene; however, trained crime-scene technicians can collect, preserve, and document insect evidence from the body and surrounding area for later examination by a forensic entomologist. This article summarizes how this should be done. Photo illustrations