Marks on a dead body could indicate violence and therefore murder. But they might have been made by legions of insects. A forensic scientist has built up data that will be a big aid to detectives faced with investigating gruesome discoveries.

A forensic scientist is unmasking the planet's tiniest criminals -- minute creatures who contaminate crime scenes and threaten to throw detectives off the scent.

Italian-born Dr Stefano Vanin, who lectures at the University of Huddersfield in the UK, is making valuable discoveries which will enable crime scene investigators to determine whether injuries to a body or damage to a corpse's clothing were caused by a human killer... or were the work of insects which moved in after death had taken place.

Very often, says Dr Vanin, tiny creatures can cause lesions to a dead body which closely resemble injuries left by a human assailant. For example, ants which clamber over a corpse's face can deposit marks which mimic the effects of a punch.

It is vital that detectives are quickly able to separate post-mortem insect damage from wounds that were caused before death by a killer.

Dr Vanin is building up a body of knowledge about the various ways in which insects can distort crime scenes and he reports on some of his latest findings in the journal Forensic Science International. This time he investigates the damage caused to dead bodies that are found underwater, where they are preyed on by aquatic creatures.

It was the retrieval of the body of a 28-year-old man in the River Brenta, at Padova in Italy, that provided Dr Vanin with the opportunity to add another piece to his jigsaw of knowledge.

The man had drowned -- witnesses had seen him struggling in the water -- and there were no signs of injury on the body. But during the autopsy a series of small abrasions in the upper eyelids were discovered.

These were caused by large numbers of amphipods -- tiny, eyeless crustaceans which had been feeding on the body and were discovered when the corpse was pulled out of the water.

This enabled Dr Vanin and his colleagues to analyse and record the post-mortal damage caused by the amphipods. The marks were very similar to those deposited by ants on dry land.

As a result, when detectives and forensic scientists are examining future corpses recovered from fresh water, they will have data which will help explain unusual markings on the body.