By Professor Jon Silverman University of Bedfordshire

There are more than four million samples in the DNA database

Since then, there has been a sporadic debate on the issue, conducted by the police, civil liberties groups and newspaper columnists.

But as the political season resumes, there is a new intensity to the argument because the government is seeking to lower the threshold of offences for which a DNA sample can be required by the police.

Some agree with the father of DNA, Professor Sir Alec Jeffreys, that we are witnessing "mission creep".

Others point to the solving of "cold case" murders and rapes as justification enough.

Recordable offence

When the national DNA database went live in 1995, only the DNA of convicted offenders could be held on it.

Samples taken by the police during an investigation had to be destroyed if the suspect was acquitted or the charges dropped.

Britain holds DNA profiles on a higher proportion of its population - 5.2% - than any other country Prof Jon Silverman

A law change in 2001 allowed the profiles of those acquitted of certain crimes to be kept.

In 2004, fresh legislation permitted the taking of samples from anyone arrested for a recordable offence and detained at a police station.

By the end of 2005, 200,000 samples which would have been destroyed before 2001 were being retained, and figures recently published by the Liberal Democrats suggest that more than half a million profiles were added in 2006.

With more than four million samples on the database, Britain holds DNA profiles on a higher proportion of its population - 5.2% - than any other country.

By comparison, the figure for the USA is just 0.5 %.

But the argument is not exclusively about numbers.

'Troubling logic'

Figures compiled from Home Office statistics and census data show that almost two in every five black men have their DNA profile on the database.

That compares with 13% of Asian men and 9% of white men.

Lord Justice Sedley's call for universal inclusion seems to be a way of tackling that disproportionality, but Ben Bowling, Professor of Criminology and Criminal Justice at Kings College, London, said this was an example of "warped and troubling logic".

You either go forward to a universal database, which I think would be wrong, or you go back Roger Smith, Justice

"You could make the same argument for other coercive powers, such as stop and search. Extend them to everyone and you end discrimination. But the onus has to be on the state to justify extending such powers," Prof Bowling said.

Roger Smith, director of law reform body Justice, said the only merit to Lord Justice Sedley's argument was that the present position was untenable.

"You either go forward to a universal database, which I think would be wrong, or you go back.

"I want a return to the 1995 position where samples could be kept on the convicted only."

However, a former chief constable said he believed the vast majority of people were ready to accept an expansion of the DNA database "in the cause of fighting crime".

Juveniles

Some countries, such as France and Canada, have legislated to prevent the retention of DNA samples from those acquitted of crimes.

The police are also required to destroy samples taken from juveniles once they have reached adulthood if they have committed no further offences.

In Britain, there is a discretion to remove a sample, but it is rarely exercised and the police insist that a growing number of cold cases have been solved because technological advances have enabled older samples to be re-examined.

Lord Justice Sedley has long been known as a liberal judge so it is perhaps surprising that this view should come from him.