The paper method can take hours to check by eye

The force's fingerprint expert can then search either the local database - containing the prints of those convicted in, for example, Nottinghamshire - or the national database of 5.5m prints.

The computer then comes up with a number of prints which are similar to the impression.

It works by picking out key characteristics in the offender's fingerprint - ridges, swirls and other marks - and searching for prints which have the same features.

The match is then double-checked by the fingerprint expert.

DNA database

According to Nafis' providers, Energis, the system is secure and cannot be accessed outside police computers.

It has been gradually introduced to forces since 1997 and all 43 forces in England and Wales should have access to Nafis by the end of April.

Areas which already have the system are now scanning in their paper records.

Similar technology has been used in Jamaica to check those who turn up to vote are the same people listed on the electoral register.

Home Secretary Jack Straw caused controversy in January when he put forward proposals to extend the police DNA database - a separate system to Nafis - to include samples from all suspects, whether or not they were eventually convicted of a crime.