Drivers who get stopped by the police could have their fingerprints taken at the roadside, under a new plan to help officers check people's identities.
No two fingerprints have ever been found to be identical on databases
A hand-held device being tested by 10 forces in England and Wales is linked to a database of 6.5m prints.
Police say they will save time because people will no longer have to go to the station to prove their identity.
Officers promise prints will not be kept on file but concerns have been raised about civil liberties.
Bedfordshire are the first force to use the equipment, which is being distributed among the forces in Essex, Hertfordshire, Lancashire, North Wales, Northamptonshire, West Midlands and West Yorkshire, as well as to British Transport Police and the Metropolitan Police, over the next two months.
Officers will scan a vehicle's number plates using a special camera that checks if the car is subject to an offence, like being uninsured.
If the driver does not convince police he is giving them a correct name, they will fingerprint him and verify his identity on the spot, instead of taking him to the police station.
Police Minister Tony McNulty said: "The new technology will speed up the time it takes for police to identify individuals at the roadside, enabling them to spend more time on the frontline and reducing any inconvenience for innocent members of the public."
Under the pilot, codenamed Lantern, police officers will be able to check the fingerprints from both index fingers of the suspect - with their permission - against a central computer database, with a response within a few minutes.
"The handheld, capture device is little bigger than a PDA," said Chris Wheeler, head of fingerprint identification at the Police Information Technology Organisation PITO.
WHY IS A VEHICLE STOPPED?
A police car installed with a camera which has an automatic number plate recognition system scans passing vehicles
The number plates are then matched against a database of offending vehicles
The database alerts the officer of a "positive" match and the vehicle is stopped
"Screening on the street means they [police] can check an identity and verify it."
Currently an officer has to arrest a person and take them to a custody suite to fingerprint them.
The device will be used with the Automatic Number Plate Recognition team, who identify vehicles of interest.
If a vehicle is stopped, police will be able to identify the driver and passengers. At present about 60% of drivers stopped do not give their true identity.
Bedfordshire Police said officers using the device in Luton on Wednesday had arrested a man suspected of being an illegal immigrant and a woman for driving a stolen car.
Inspector Steve Rawlings said it takes two sets of fingerprints and the fingerprints are not retained.
The first positive criminal fingerprint identification was made in Argentina in 1892
The UK's first fingerprint bureau was founded in 1901
No two fingerprints have ever been found to be identical on a database
"The encounter can be 15 minutes on the roadside rather than three hours in the police station," he said.
The device has an accuracy of 94-95% and will be used for identification purposes only, say police, and there are electronic safeguards to prevent misuse.
It sends encrypted data to the national ID system using GPRS - a wireless system used by many mobile phones.
More than 6.5 million fingerprints are cross-referenced and sent back to the officer.
Mark Wallace, who represents the civil liberties group the Freedom Association, told BBC Radio Five Live that he had "concerns" about the scheme.
"I don't think we should be reassured by the fact that at the moment it's voluntary and at the moment they won't be recorded," he said.
"Both of those things are actually only happening in the trial because the laws haven't been passed to do this on a national basis compulsorily and with recording."