DNA in the dock.

Questions the reliability of DNA fingerprinting in criminal trials with reference to the Thomas Schwarz case in the U.S. in which cross-contamination at the Cellmark laboratories gave a false result. The programme shows how laboratory errors can be made. It examines the method used by the UK National DNA Database, which involves the polymerase chain reaction - a system devised by Kary Mullis for which he was awarded a Nobel Prize - and finds that its method of increasing accuracy actually increases the risk of contamination. As the UK National Database gets larger, so the chance of error and random match increases. Among those taking part in the programme are Prof. Alec Jeffries (inventor of DNA fingerprinting) and David Werret (head of the UK National Database).