Eight years ago, police investigating the robbery of a 71-year-old Tasmian woman found a leech at the home. They took a blood sample from the leech and now have used DNA gleaned from the sample to convict Peter Alec Cannon of the crime. He has since admitted guilt.
From the BBC News:
Wikimedia Commons image
When police came to investigate the robbery, officers found a leech near the safe, and the resulting DNA sample was recorded in the Tasmania Police DNA offender database.
Cannon would probably have got away with the crime had he not been charged with drug offences late last year, and asked to give a DNA sample - which matched that from the crime scene.