DNA is a unique identity code for every living organism on the earth, and if you have enough information about the source, and you find a sample in a place, with a simple DNA test you can find the relationship between source and sample.

At a crime scene, urine may be used to identify the perpetrator of a crime, or to place a victim at a particular site. In a laboratory, DNA analysis may be needed to positively identify an individual as the submitter of a particular urine sample, especially in the case of a contested positive sample.