Experimental validation of forensic evidence: a study of the decompositionof buried pigs in a heavy clay soil

In a murder investigation, where the victim had been strangled and buried i n a shallow grave, there were discrepancies between the post mortem interva l (PMI) as estimated from entomological studies and estimations determined from other evidence. This inconsistency provided the impetus for examining the decay process using pig carcasses as analogues for the human cadaver. T he pigs were buried in the immediate vicinity of the original burial site i n December 1996, which was the month when the victim was purported to have been interred in the previous year. The buried pigs were then monitored for 5 months which, based on the evidence other than the entomological, was th e period over which the corpse was thought to have lain in the ground. The pig corpses were disturbed by scavengers in mid April: this was the same ti me that the human corpse was discovered in the previous year by scavengers. Insects played no role in the decomposition process until the pig carcasse s had been exposed by animals. Blowflies, notably Calliphora vomitoria, wer e attracted to the exposed tissues and laid eggs from which larvae develope d. Calliphora vomitoria is a species often used to estimate PMI. This inves tigation has shown that soil conditions and low seasonal temperatures had p reserved the pig carcasses for longer than might be expected. Using the blo wfly larvae to estimate PMI would have produced erroneous results had not t he burial environment and exhumation history been investigated. (C) 1999 El sevier Science Ireland Ltd. All rights reserved.