Only small amounts of DNA are found at a crime scene. The technique that uses an enzyme to replicate DNA regions from a small sample of DNA for use in DNA fingerprinting is PCR (polymerase chain reaction)
PCR is used as a tool in genetic fingerprinting. This technology can identify a single person from among a million others. Once a tiny DNA sample from a crime scene has been amplified onto numerous copies by PCR, the DNA can be compared with a DNA database or with DNA from suspects to identify or rule out suspects during a police investigation.