DNA is a double-stranded chain of molecules found within the nucleus of every cell of every organism. The sequences of molecules in the DNA chain function as a unique genetic blueprint: they constitute a genetic code that determines the structure and function of each part of the organism. The DNA in each individual remains the same no matter where in the body it is found. DNA samples taken from different individuals can be distinguished and compared by analyzing lengths in the DNA chain that differ from person to person. DNA analysis has great promise for criminal identification and for establishing an individual's parentage. To date, three techniques for DNA identification and typing have been developed by commercial laboratories. Although DNA typing has great forensic potential, it has not yet been proved to be a thoroughly accurate and reliable test. Claims that a DNA typing test can 'identify individuals without a doubt' are exaggerations. It is also possible that two unrelated people may have identical prints because they have DNA lengths or patterns that are similar. Therefore, false identifications are possible. Before DNA typing can become an accepted forensic tool, additional validation studies must be done.