Even with today's technology, the perfect murder was still possible, but you'd have to have a stomach for maggots, according to forensic entomologist Dr James Wallman.The size of the maggots on a body indicates their age, providing a potentially accurate time of death.Dr Wallman, a senior lecturer in the University of Wollongong's School of Biological Sciences, said that in order to distort the time of death and concoct an iron-clad alibi, "fiddling with the maggot evidence" might be the key.But the killer would have to be extremely skilled to mislead a forensic investigator, especially one of the calibre of Dr Wallman, who has studied insects for most of his life and assisted police with more than 70 cases over the past 20 years."If you were going to try and bamboozle someone like me, you would grow up some specimens (maggots) ... You'd put them on the body and they might suggest a certain age or time since death that was different from the real time," Dr Wallman said.But "growing up" maggots was an acquired skill."They could be grown on a sheep's liver and then placed on the dead body. But you'd have to be careful because the state of decomposition could also betray the reality."Dr Wallman said a lawyer had previously tried to discredit his evidence in court by suggesting the maggots on a body had come from elsewhere."He said to me, 'How do you know there wasn't a dead sheep in the adjacent paddock and a fox had come along, ate some of the sheep along with the maggots and then wandered over to the dead body and vomited the maggots on to the body?' "But modern technology has the answer - an autopsy on the maggot would determine whether sheep DNA was present.Aside from the maggots, deaths in a built environment differed from those of the bush, enabling investigators to determine whether a person was killed in one place and then relocated.In the past 30 years, nine bodies have been found along the Illawarra escarpment and seven in the Ivan Milat killing grounds of Belanglo State Forest.Most were found to have been killed in suburbia and later dumped in the bush.