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Maggots to give crime scene clues

August 21, 2003

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Flies are often first to arrive at a crime scene and the larvae they leave behind could now help to secure more convictions thanks to an Australian-developed DNA test for maggots.

Forensic entomologists have long been able to help police solve murders by studying maggots and other scavenging insects to determine the time of death and also whether someone had returned to a corpse to bury or move it.

The creeping, organic recyclers have gruesome secrets to tell after-the-fact, but in the case of flies, even experts find it difficult to distinguish between types of maggots.

Currently, corpse larvae may have to be reared to adult stage to confirm their species, thus holding up police investigations.

But Michelle Harvey, a PhD student from the University of Western Australia's Centre for Forensic Science, has been working on a new DNA test for maggots that will speed up the identification process.

"If you know how big the maggot is and what species it is, you can estimate how old it is, how long it's been on the corpse and how long the person's been dead," Ms Harvey told AAP.

"The problem is that, in different places, many different species of insects are involved - and these develop at different rates.

"I've developed a new DNA fingerprinting technique, based on the DNA of the maggot, meaning that we can work out what species we're dealing with and estimate time of death within 48 hours of taking specimens from a corpse."

Within a year, she hopes the DNA technology will also be able to pinpoint which population of flies the maggots descended from to help guide police to the place of death when bodies have been shifted by murderers.

About 18 fly species are commonly found on corpses in Australia, and they start laying maggots about four hours after death.

Ms Harvey said offenders were unlikely to be convicted by the evidence of maggots alone, but they contributed to the bank of scientific facts that were needed to persuade juries.

Her supervisor, Associate Professor Ian Dadour, has worked on about 110 crime cases since 1989, with nearly half of those proceeding to court.

In 1997, police found a man's body in a burning house in suburban Perth.

The fire was extinguished on a Saturday but a drum was found in the house containing accelerants and a blood-stained quilt which had attracted maggot deposits which were not completely destroyed in the fire.

Based on the maggots, the time of death was traced back to the previous Wednesday.

©2003 AAP

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