Detectives Use this Simple Technique to Find Your Fingerprints (Even AFTER You Have Wiped Them Off)!

There’s a common movie trope of an actor wiping their fingerprints off a gun. It seems like a simple wipe with a cloth eliminates any trace of a criminal’s guilt, but that isn’t actually the case!
Scientists have developed a method that can visualize prints from even the faintest fingerprint deposits left after the metal of a gun is wiped off. This technique uses a colored-electro active film that uses fingerprint residues as a stencil for blocking the electric current. Once a voltage is passed through, the oily regions deflect the colored substances surrounding bare regions, which gives rise to a negative ridge pattern.