Insects play important role in helping to solve crimes

Insects play an increasingly important role in helping to solve crimes through their presence in, or interaction with, evidence. It is emerging as a science in its own right, forensic entomology.

Dr Martin Hall, a research entomologist at Britain's Natural History Museum, discussed the contribution made by forensic entomology yesterday during sessions at the British Association for the Advancement of Science's annual Festival of Science in Sheffield.

"Basically it is applying insect evidence to solve crimes," he said. It could be gruesome, for example, the presence of maggots on a hidden corpse, which in turn could provide clues as to when a person died. It was being used, however, for a much wider selection of crimes, he said.

A forensic entomologist might be asked by a court to confirm whether holes found in alleged antique furnishings were made by a drill or woodworm. Insects recovered from stored cannabis might show whether it was opened and handled in the country where it was discovered or only in the country where it was grown.

Dr Hall said the use of entomology in solving crimes had been known for 100 years. Its first success in the UK was in 1935 when a man was found guilty of killing his wife and her partner. The murderer claimed an alibi that did not match the forensic evidence provided by maggots growing on the two bodies. He was convicted and hanged.

The most important insect observed by forensic entomologists was the blowfly, which responded quickly to the odours of corpse decay, often within a few hours of death. Scientists have studied its lifecycle in detail and, by determining the stage to which the blowfly larvae developed, the insects could provide accurate information about the approximate time of death.

This was not always absolute proof of when a crime occurred, he said. A body could first have been frozen and held before dumping, but this would not be typical of most murders where the victim was either moved and dumped soon after death or abandoned at the scene of the crime. A refinement of this might come in the future with DNA profiling, he added.

There might be slight genetic differences between blowflies in northern England compared to the south for example. The larvae might therefore also provide clues about where a crime occurred.

Britain's National DNA database, set up in 1995, now holds 600,000 DNA genetic fingerprint samples, said Dr Peter Gill of the UK's Forensic Science Service.

This increased by about 200,000 a year. DNA fingerprinting had become so accurate that a match could be made with as little as a single flake of dandruff, he added.