Forensic entomology applies insect evidence to legal problems. Compared to the traditional procedures in Forensic Medicine, insects are accuracy even in advanced stages of decomposition (after four to five days postmortem) when postmortem phenomena such as autolysis and putrefaction occur. Flies from the family Calliphoridae are the first group that arrive to the cadaver, and attract by the odor produce during the early stages of decomposition. Since they lay eggs on a carrion within minutes after death, the estimation of the age of the oldest present eggs, larvae or pupae will provide a minimum postmortem interval (mPMI).
Insect species associated with carrion and the period of life cycle vary according many factors, one of the most important being the geographic region or bio-geo climatic zone. The bio-geo climatic zone includes the habitat, vegetation, soil type and meteorological conditions of the area. Therefore, knowledge of the insect fauna that are attracted to human cadavers in every geographical region is fundamental for the use of flies as forensic indicators, and databases should be developed. This sort of information is obtained from field experiments on carrion decomposition, usually made with animal models.