DNA

Forensic scientists can use DNA in blood, semen, skin, saliva, or hair at a crime scene to identify a perpetrator.
This process is called DNA profiling.
DNA profiling was developed in 1984 by British geneticist Sir Alec Jeffreys, and first used in forensic science in 1988 to convict a certain Colin Pitchfork for the murder of two girls in Leicestershire, UK.