Amino acid test

In April 1993, a man in a balaclava mask escaped after sexually assaulting a 36-year-old woman in the town of Bridgwater, England. More than 13 years later, forensic detectives used an unusual approach to track the man down: A genetic trace that led first to his sister.

Known as familial searching, the U.K. technique has already helped crack 20 difficult cases and led to the arrest of several long-elusive murderers and rapists.

The innovation is propelled by the growth of Britain's DNA database, which holds the records of 4.2 million people in England and Wales, or nearly 8% of the population there, one of the largest proportions in the world. Anyone arrested -- including for minor offenses -- must provide a DNA sample, which stays in the database permanently, even if the person is acquitted. About a quarter of the profiles are of minors, some as young as 10.

The U.S. is now considering following Britain's lead...

The Gene Police (Wall Street Journal, 23 February 2008)