Mafia Manicure

In the days of Al Capone, when Mafias were very common, they had methods of disposing of evidence. To avoid leaving fingerprints, it was common to burn their hands with sulfuric acid to burn away the surface and leave them without fingerprints.

Police Officer 1: We couldn't find any prints on the body of the homicide victim
Police Officer 2: The killer was either wearing gloves, or had gotten a Mafia Manicure