Recovery & identification of human Y-STR DNA from immatures of chrysomya albiceps (Diptera: Calliphoridae). Simulation of sexual crime investigation involving victim corpse in state of decay.

The number of sexual crimes in Brazil, as in several other countries, is very high. In many of these crimes the women raped are murdered and their bodies are found days later, in an advanced state of decomposition, with intense cadaverous fauna. Forensic Entomology studies insects and other arthropods that can be used in the expert analysis of various types of crimes. Diptera, the order of insects that comprises the two-winged or true flies, represents one of the largest known groups of insects and is the principal source of cadaveric entomofauna. Members of its Calliphoridae family are observed in cadavers in all phases of decomposition. The retrieval and identification of human Y-STR DNA from the gastrointestinal tract of Calliphoridae species Chrysomya albiceps maggots and pupae can provide a good tool for the gathering of evidence in sexual crime investigations involving rape and death, in which the abandoned victim's body is found in a putrefied state. In this study, the animal model used was a female pig, Sus scrofa, which was sacrificed in a forested area with three shots from a 0.40 calibre Taurus pistol, and inoculated with semen to its anal and vaginal regions, simulating rape and homicide. During decomposition, 20-80 maggots were collected every 24 h and preserved in 70 % alcohol, totalling 289 maggots and 157 pupae (446 immatures) over a period of 14 days (336 h) of decomposition. Each maggot was then dissected for removal of the digestive tract, which was placed in extraction buffer. The molecular phase proceeded with extraction, quantification, amplification and capillary electrophoresis of samples, testing 16 STR loci of the Y chromosome. It was possible to establish a partial Y-STR DNA profile, with the amplification of up to eight sites, by considering a combination of the samples taken at hours 144 h, 168 h, 192 h, 216 h, 240 h, 288 h, 312 h and 336 h.