In 1903, a prisoner named Will West (above) arrived at Leavenworth. The record clerk took one look at West's mugshots and insisted that he had seen him before. West disagreed and said that he had never been to Leavenworth before.
The clerk, however, was sure that he had seen West's mugshot before and retrieved the file based on West's measurements. Inside, was the mugshot below. When he showed it to West, he was confused. He said, "That's my picture, but I don't know where you got it because I've never been here before!"
As amazing as it sounds, West was telling the truth. He had never been to Leavenworth before. The man in the mug shot had the exact same measurements as west and was virtually identical. As a matter of fact, if this wasn't eerie enough, the mysterious twin, serving time at Leavenworth, was also named William West.
The incident called the reliability of Bertillion measurements (the then-accepted means of identifying people) into question, and it was decided that a more positive means of identification was necessary. You can then thank these two lifers named William West for helping to usher in the age of fingerprinting.
Source ; http://slightlywarped.com