A minor scrape, scratch or even burn won’t affect the structure of the ridges in your fingerprints — new skin reforms in its original pattern as it grows over the wound. But each ridge is also connected to the inner skin by small projections called papillae. If these papillae are damaged, the ridges are wiped out and the fingerprint destroyed.

Some criminals have tried to evade capture by tampering with their own fingerprints. Chicago bank robber John Dillinger reportedly burned his fingertips with acid in the 1930s. Recently, a man in Lawrence, Mass., tried to hide his identity by cutting and stitching up all ten of his fingertips (fortunately, a police officer recognized his face).

But as fingerprint technology becomes a common form of authentication from bank vaults to luxury cars, law enforcement officials worry that would-be criminals might try to steal entire fingers for the prints. In one case, robbers in Malaysia cut off a man’s fingers so they could steal his Mercedes. Companies that make biometrics security equipment realize the potential dangers of this system, and are now creating scanners that detect blood flow to make sure the finger is still alive.