Why is DNA evidence so reliable in determining the identity

the analysis of genetic material taken from small samples of blood, semen, hair or tissue, is based on the idea that each person's DNA is unique.

DNA is the chemical that forms genes, and the fingerprinting technique relies on the fact that each individual has a characteristic pattern of DNA. By chopping up DNA and then lining up the resulting fragments, scientists can detect differences in fragment lengths, which would show individual variations. To see if the samples are from the same person, scientists check to see whether particular fragments are exactly the same length.

Explanation:

it other words our fingerprints and genes are unique to a single person