A leech has proved the key to solving an eight-year-old aggravated robbery case in northern Tasmania.
Police believe a blood sample from a leech used to identify a criminal is a world forensic first.
DNA taken from blood in a leech was used to identify a man who on Monday pleaded guilty to robbing a 71-year-old woman at her home in September 2001.
Peter Alec Cannon, 54, from Lilydale and another person, who has not been caught, poked the woman with sticks and robbed her of $550, the ABC reports.
The blood sample taken from it did not match anyone who attended the scene, or the victim of the robbery, so it was filed away.
But last year Canon's DNA was matched to the sample taken from the leech after he was charged with drug offences.