Before fingerprints became the standard way to catch criminals, police used a much more complicated method called Bertillonage.

In the late 1800s, a French investigator named Alphonse Bertillon realized that while criminals could change their names or wear disguises, they couldn't change the size of their bones. He created a system to track "recidivists"—which is just a fancy word for "repeat offenders."

When someone was arrested, the police wouldn't just take a photo. They would use special tools to measure 11 different parts of the person's body, such as:

* The length and width of the head.

* The length of the left middle finger.

* The length of the left foot.

* The reach of their outstretched arms.

The system worked great until 1903, when a man named Will West was sent to Leavenworth Prison. The record clerk was confused because he was sure Will had been there before.

When they took his measurements, they matched a man already in the prison named William West. Not only did they have the same measurements, but they looked almost like identical twins! However, they were two completely different people.

The "Will West" case proved that body measurements weren't unique enough to be perfect. This failure led police to stop measuring bones and start looking at the tiny ridges on the tips of people's fingers.