Genetic fingerprinting, DNA testing, DNA typing, and DNA profiling are techniques used to distinguish between individuals of the same species using only samples of their DNA. Its invention by Sir Alec Jeffreys at the University of Leicester was announced in 1985. Two humans will have the vast majority of their DNA sequence in common. Genetic fingerprinting exploits highly variable repeating sequences called microsatellites. Two unrelated humans will be likely to have different numbers of microsatellites at a given locus. By using PCR to detect the number of repeats at several loci, it is possible to establish a match that is extremely unlikely to have arisen by coincidence, except in the case of identical twins, who will have identical genetic profiles.

The DNA testing method in most common use today is called "short tandem repeats," or STR. Large sections of human DNA are identical--the individual differences (called polymorphisms) occur in small segments of the DNA chain, usually at the same location on the chain. The STR testing process looks for patterns at 13 specific DNA sites where these differences typically occur. STR is a highly accurate DNA testing method, with the chance of misidentification being one in several billion. 

Genetic fingerprinting is used in forensic science, to match suspects to samples of blood, hair, saliva or semen. It has also led to several exonerations of formerly convicted suspects. It is also used in such applications as identifying human remains, paternity testing, match organ donors, studying populations of wild animals, and establishing the province or composition of foods. It has also been used to generate hypotheses on the pattern of the human diaspora in prehistoric times.
 
Testing is subject to the legal code of the jurisdiction in which it is performed. Usually the testing is voluntary, but it can be made compulsory by such instruments as a search warrant or court order. Several jurisdictions have also begun to assemble databases containing DNA information of convicts.

In a related field, DNA testing is now applied to the identification of human remains. DNA analysis has proven to be much more powerful than other methods of identification, especially in cases where the body has been badly damage in a fire or an accident, or if the body is decomposed.

A rapidly expanding area of DNA testing use is in paternity testing. In virtually all cases, the mother of a child is known without the need for any sort of testing. But it is possible for the relationship between father and child to be called into question. By sending a sample of their DNA (along with a sample from their supposed offspring), fathers can determine the true nature of the relationship without doubt.
 
The United Kingdom currently has the most extensive DNA database in the world, with well over 2 million records as of 2005: The National DNA Database (NDNAD). The size of this database, and its rate of growth, is giving concern to civil liberties groups in the UK, where police have wide-ranging powers to take samples and retain them even in the event of acquittal.

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