Two hundred kilometers north of Hobart, Tasmania, on a late September afternoon in 2001, two men broke into the rural home of 71-year-old Fay Olson. The intruders—armed with sticks and wearing black hoods—ransacked Olson’s home, forced her to open a safe, stuffed AU$550 into a pillow sack, and fled into the bush surrounding the house. They left Olson tied up with a belt cinched around her ankles. The pair made off with their loot scot-free, but one of the perpetrators inadvertently left something behind that would spell his undoing 8 years later: a leech, swollen with his DNA-filled blood.
Tasmanian investigators found little in the way of evidence that could tie the criminals to the crime, but one of the officers on the scene noticed a bloated leech wriggling next to the pilfered safe. He collected the parasite—likely Philaemon grandis, endemic to Tasmania—as the lone piece of evidence that might ...
