The French forensic scientist Edmond Locard devised the idea that “every contact leaves a trace” in 1920, and this became known as the “Locard Exchange Principle.” Earlier, he also established the world’s first crime laboratory, in Lyon, France, in 1910. Two years later, he solved a difficult murder case of a woman who had been strangled. The woman’s boyfriend, Emile Gourbin, a bank clerk, seemed to have a perfect alibi, but Locard examined his fingernails and found minute scrapings of skin still containing the pink dust of the woman’s face powder. The revelation prompted Gourbin to confess.