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19 May 2000 00:00
THE day before Good Friday a 33-year-old man was convicted in the Johannesburg Supreme Court for the abduction, indecent assault and murder of an eight-year-old girl.
Besides the appalling nature of the crime, this case stands out for three reasons: the criminal was caught, received only a 31-year combined sentence and, most remarkably, the case also marked the first time in South African history that entomological findings were presented in court and used as evidence that aided in the conviction of the suspect.
"It is easy to commit the perfect murder," says entomologist Dr Mervyn Mansell of the Plant Protection Research Institute in Pretoria.
This is generally not a reassuring statement. It is even less so when it comes from a man who since 1997 has been called in to help the police with more than 100 of South Africa's most gruesome crimes.
The police, especially in this country, are very busy people.
The study of insect evidence can be used to uncover circumstances of interest to the law that are often related to crime. This is known as forensic entomology and it is a growing field of science in the United States, Europe and, more recently, in South Africa.
Dr Martin Villet, of the Rhodes University entomology department, explains that forensic entomology can be divided into three different types and uses. Domestic forensic entomology deals more with urban issues, including delusional parasitosis. This is a condition where the individual concerned has the mistaken belief that they are infested by parasites, including mice, lice, fleas, spiders, worms, bacteria and other nasties.
Forensic entomology's most lucrative aspect is concerned with the presence of insects in commercial and industrial enterprises. Villet takes great glee in revealing that most Americans are oblivious to the knowledge that, in the US, it is permissible to have as many as 30 cockroaches in one chocolate bar.
However, it is medico-criminal forensic entomology that arouses public morbid fascination. Each stage of decomposition on a corpse is characterised by different insects and arthropods. By studying this succession of insects, a forensic entomologist has the possibility of being able to determine the post-mortem interval (PMI), the site of death and perhaps even the cause of death of a victim.
Determining the PMI of a body is of crucial importance in murder investigations. In July last year the decomposing body of a young girl was found in the veld seven weeks after she went missing. The eight-year-old girl had disappeared while being looked after by her neighbour. The suspect, Albert du Preez Myburgh, the neighbour's son, had been charged with the girl's abduction shortly after she disappeared. When the body was discovered he was also charged with indecent assault and murder of the victim.
Although Myburgh admitted to kidnapping the girl and "fondling" her, he pleaded not guilty to murder, maintaining that he was in jail when she died. This claim was refuted by evidence presented in court by Mansell, who was able to determine the PMI from insect specimens collected from the girl's body. One of the flies found, the Winter blow fly, is unique in that it has a long life cycle (up to eight weeks) and it lays eggs only in the shade. This insect evidence enabled Mansell to determine the time of death, which happened to correlate with the time the girl went missing. These findings corroborated with other evidence to find Myburgh guilty of murder.
This case has proved to be a perfect example of how the determination of a PMI, through entomological findings, can lead to the conviction of the murderer.
In serial killings a PMI is also fundamental in establishing a psychological profile of the killer. The PMI can indicate if the killer has any particular trends, such as killing only during specific phases of the moon, at weekends or is entirely opportunistic.
In South Africa forensic entomology has proved to be very useful in providing information regarding the prolific cash-in-transit van hijackings. "Just from identifying the bugs in the radiator, you can determine how far the vehicle has travelled, where it has been and even if it has travelled more at night or more during the day. Put simplistically, if there are more locusts and butterflies stuck in the radiator, the car traveled more in the day. Moths, mosquitoes and midges show that the vehicle travelled more at night," says Villet.
Forensic entomologists are few and far between, but that hasn't stopped them from trying to elbow their way through the crowds of crime-scene photographers, forensic pathologists and DNA specialists associated with murders. "It's all about marketing," says Mansell enthusiastically. "The police and even the mortuary staff have to stop seeing revolting little wriggling and crawling insects that have to be washed off the body as soon as possible, and start seeing these maggots and beetle larvae as serious forensic evidence."
For the past few years, Mansell has been giving two to three lectures a month at police training colleges in an endeavour to increase police awareness of the importance of forensic entomology in crime-scene investigations. "I tell them [the police] about insects. I show them the decomposition process and how it can be used to determine the PMI. I show them how to take samples and I give them examples of successful cases where the entomological information was fundamental in solving the crime."
Mansell's marketing has been successful in that there should now be very few policemen out in the field who do not know about forensic entomology.
Another necessary reason for this marketing campaign is to provide funding. After Mansell had been called in to help on the grim Moses Sitole case in 1997, he managed to acquire funds from the Department of Arts, Culture, Science and Technology as part of the National Crime Prevention Strategy. These funds are not used only to pay for the police and university lectures but also to support the crucial research being done at the University of the Free State and Rhodes University, the only tertiary institutions in South Africa which offer forensic entomology courses.
Dr Theunis van der Linde of the University of the Free State is conducting research on the effect of burning corpses on maggots. Yet, how does one experiment with burnt human flesh? In South Africa you don't; you use pigs. Pig flesh is very similar to human flesh in that it is not very hairy and has a layer of fat under the skin. The problem lies in acquiring pigs. "It is a very sensitive issue. But please note that only pigs that were already marked for human consumption and are then condemned are used," says Mansell.
Research on the effect of different temperatures on maggots is one of the many aspects of forensic entomology that is being studied at Rhodes University. There are also many student projects that are making valuable contributions to the science. Eunice Musvasva, a Rhodes University graduate, deliberately poisons maggots. "Maggots grow more slowly if you feed them a greater concentration of barbiturates. But if you feed them steroids they grow faster than normal," says Musvasva.
"You can often tell when an individual has died from a cocaine overdose," says Villet, "because the maggots in the nasal cavities will be a lot larger than usual."
A computer program that will help policemen identify the various insects on a corpse and decode their forensic message is being compiled by Angela Bownes, an entomology masters student at Rhodes. This program, known as Identifly, is expected to be released this year and may even be used in conjunction with an electronic database that is being set up by Mansell. The database will contain all the graphics and information collected from past cases.
Mansell is also compiling a forensic entomology handbook to aid policemen in crime-scene investigations. It will include colour pictures, insect life cycles and information on how to take samples. With extra funding, Mansell would also like to manufacture forensic entomology crime-scene kits, which will also assist the police in taking insect samples.
It is obvious why Mansell is regarded by his colleagues to be a pioneer in the field of forensic entomology. But it is a watershed event for forensic entomology in this country that this high esteem has overflowed into the courtroom. As Mansell says of his time in the witness box, "It was an exhilarating, tough and enriching experience. But most importantly, it provided the logical outcome of forensic entomology."
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