Fingerprints consist of oil, sweat and skin cells, which leave behind an impression of the unique ridges and whorls of each finger. The chemical composition of a fingerprint can also reveal suspect habits, like smoking or what aftershave or perfume they use.

The method was devised in the 1800s and made its court debut in 1902; from there it slowly rose to fame as a failsafe way to catch crooks. Today’s evidence show that this method doesn’t deliver each time. A shocking 20% of the time fingerprints are mismatched!

In the past, forensic scientists also linked the scratches and dents in bullet casings with the gun’s that fired them by using ballistic fingerprinting. This method was shown to be fatally flawed in 2002 and suspended in 2005.

Scientific methods used for putting criminals behind bars flawed? That’s not something we like to hear, is it? But there’s hope – criminology changed forever with the DNA revolution. But more on that tomorrow...