DNA testing offers the potential of examining microscopic variations that make human beings, except for identical twins, verifiably unique to a statistical certainty. This power of identifying is valuable not only to the police but also to the wrongly accused. The FBI plans to open its own DNA identification laboratory this winter, and an FBI deputy assistant director calls it perhaps the most significant development in identification in this century. Almost any tissue sample can be tested, including bone, blood, semen, skin, and hair containing the root. Noncellular body fluids like saliva, urine, and sweat can also carry testable quantities of DNA. However, DNA analysis does not work for miniscule samples, but its nearly 100 percent certainty makes it far superior to other techniques that offer only a 90 to 95 percent level of certainty. DNA testing has proved to be particularly useful in conjunction with other forensic testimony. However, many experts caution that it will not have a dramatic impact on overall criminal conviction rates, but will be most useful in solving sex crimes. If the legal and scientific issues it has raised are solved satisfactorily, its future in police work may be restricted only by the scientists' imaginations.