Blood taken from a leech found at an Australian crime scene was used to catch an armed robber eight years after his crime, in what officials claimed to be a forensic world first.

The engorged bloodsucker was found beside a safe at the ransacked home of an elderly woman in Tasmania, Australia's southernmost state, following a 2001 break-in.

"It was the only evidence we found, and as there was no evidence of any leech bites from the victim or the police present we thought it was a good chance to have come from one of the offenders," said Detective Inspector Mick Johnston.

Police took a sample of the blood for DNA profiling, and when the robber was DNA tested over drug offences in late 2008 Johnston said they found a match.

"It is the oddest way of convicting anyone I have ever been involved in," Johnston told the Hobart Mercury newspaper.

"I have not been able to find any similar cases anywhere in the world ? nothing like this at all."

The bitten burglar, Peter Alec Cannon (54), pleaded guilty to the robbery which netted $550.