A bug's life on the body farm
Grissom looks puzzled — The corpse on the gurney is semi-decomposed and the coroner is battling to get to grips with what happened.
This is a typical scene from the TV series CSI, which follows the sometimes gruesome adventures of a team of top forensic pathologists. And as anyone who watches CSI will tell you, the most important things in a murder investigation are determining the time, place and manner of death.
But what television doesn’t tell you is that, more often than not, the heroes of crime scene investigation are not even human — they are insects.
Enter the forensic entomologist. A person who helps to solve murders, by studying corpses and the insects that feed on them.
Yes, it sounds grim, but forensic entomology is a vital and fast-growing field of research. In South Africa the field is dominated by three experts. Mervin Mansell, who works for the United States Department of Agriculture’s Pretoria office, and Theunis van der Linde, of the University of the Free State, work primarily with the South African Police Service on active crime scenes. The third, Professor Martin Villet, engages in academic research at Rhodes University.
Villet will be lecturing at Sasol SciFest 2005, giving an outline of forensic entomology and what he terms the ‘six-legged flying squad” — nature’s murder detectives, namely blowflies.
He explains that forensic entomology is still very much an under-resourced and developing science.
‘In South Africa, the first case which introduced entomological evidence in court only took place in 2000,” he says.
Villet’s field of expertise is the development of blowflies in relation to temperature and drugs.
Forensive entomology can be traced back to 1920 when it was discovered that a lot of the flies that feed on dead bodies also feed on live sheep.
‘Different species of blowfly will have different effects on sheep. The ‘wrong’ type of fly will eat an entire sheep,” says Villet. ‘But the ‘right’ fly stops when it hits resistance, that is, live sheep flesh!” It is these flies that are being used in medicine to treat infected wounds and burns — their maggots eat infected and rotting flesh but leave clean, unaffected tissue intact.
There are eight different species of blowfly, or greenbottles, in South Africa. A typical lifecycle is that a fly will lay eggs that will hatch into maggots a maximum of two days later, depending on temperature and other conditions. It takes between one and three weeks for the maggots to form pupae, which pupate for 10 to 18 days, emerging as flies. The lifespan of an adult fly is about four weeks.
In murder cases, flies are usually the first insects to arrive at a corpse. Eggs are laid and maggots hatch and begin feeding on the body. Then other insects will begin to feed — beetles, for example, feed on drier muscle and skin once the body has begun to dessicate.
The process of decomposition has most famously been studied by the FBI in the United States, specifically on what is known as the Body Farm. This area of land close to the FBI’s training establishment at Quantico is home to a selection of human corpses left to the FBI for research purposes. The bodies are placed in various strategic positions on the farm for mother nature to work on. The process of decomposition and its associated insect activity is documented and the data is invaluable as a tool for solving crimes.
In South Africa there is no body farm. Legislation won’t allow one, even for bodies which have been left to medical science. So, researchers use the next best thing, says Villet — pigs.
‘A pig’s skin structure is similar to that of human beings — there is no hair and pigs are of a similar size and weight to us,” he says.
But it is not just murders that insects can help to solve. Other applications include solving insurance cases.
‘I worked on a case involving a consignment of leather which was sent to Turkey via Cape Town. When it arrived it was found that the leather had been attacked by beetles. We were able to deduce when they had infested the leather.”
Another interesting side to Villet’s research involves insects that infest stored produce. ‘If you open a packet of breakfast cereal and find it infested with weevils, you want to know whether you bought it like that,” says Villet.
It is encouraging to learn that the research being undertaken by Villet and his team at Rhodes is on par with international research.
So, have CSI and the likes of Patricia Cornwell, with her books Body Farm and Blowfly, and Thomas Harris with his Silence of the Lambs, boosted interest in forensic entomology?
Definitely, says Villet. Although the public image of the science and the scientists who pursue it leaves much to be desired.
‘We are still portrayed as geeks with thick-lens glasses and no dress sense,” complains Villet, who is a normal-looking jeans and trendy T-shirt type of guy.
But he can take solace from the fact that what he is doing is of such importance.
‘South Africa’s criminals should be worried,” he says. ‘Bugs always spill the beans. It’s extremely difficult to destroy the evidence.”
Villet is training a number of students at Rhodes who are very good at what they do. His research also made a good impact at the International Conference on Entomology last year.
‘We share techniques in this field,” he explains. ‘There’s a lot of cross-pollination across the globe. We have a major international conference coming up in Perth, Australia, next year where the latest developments in what we are doing here will be discussed.”
I’d love to be a fly on that wall!
Professor Martin Villet’s lecture takes place on Wednesday March 16 at the Monument Olive Shreiner Hall at 3.30pm