by Danny Shaw BBC Home Affairs Correspondent

DNA provides compelling evidence

Ask a detective to list the most useful crime-fighting tools available to police and they will almost certainly include the ability to take fingerprints and DNA from suspects.

Though by no means 100% accurate, fingerprints and DNA profiles provide compelling evidence of a link between a suspect and a crime scene, or a suspect and a victim.

Fingerprints, which can now be processed in minutes, can also help police verify the identity of a suspect.

So it is no surprise the move to extend powers to fingerprint and take DNA is being driven by the police themselves.

At present, their powers are limited.

If police need to test someone who has been arrested, they can only do so for the purpose of comparing their fingerprints or DNA to scientific evidence from a specific inquiry.

Authorisation is required in such cases from a senior police officer.

Under the new measures police would be permitted to take prints and samples from anyone arrested for a recordable offence.

That is 1.2 million people each year.

Open to abuse?

The information would be stored indefinitely on two national databases, which already contain 1.8 million DNA profiles and 5.5 million fingerprint records.

The concern of civil liberty groups is that the details of innocent people will be held on databases designed to combat crime.

Campaigners say there might be mistakes - people could be falsely connected to a crime.

They are also worried the system is open to abuse - samples might be planted or switched to link someone to a crime, or the genetic information contained in DNA profiles could be used for other means.

But their chief worry is the government is trying to create a central register of everyone's DNA, by the back door.

It is true the database has expanded rapidly, but discretely.

From a bank of profiles of convicted offenders and crime scene samples, it now includes those charged with crimes but acquitted, as well as samples taken voluntarily during mass screenings to help solve rape and murder inquiries.

The Home Office denies it is surreptitiously building up a database of every citizen's DNA.

And it will only take samples from people who are arrested.

But the danger of expanding the database in such a way is that certain sections of the population - ethnic minorities in particular - will be disproportionately represented.

At 8%, the proportion of black people arrested is five times greater than the proportion in the population as a whole.

Asians are also disproportionately arrested.

Call for debate

That is one reason why the inventor of DNA testing, Professor Sir Alec Jeffreys, believes a database should include everyone.

The government is not yet prepared to take that step.

But with the technology ever more reliable and with heightened concern about crime and terrorism, there are growing calls - led by the police - for a serious debate on the issue.

Clearly not this year, possibly not this decade, but probably in the next 20 years, the arguments in favour will outweigh those against.

When that happens, babies will be pin-pricked at birth and mouth swabs will be taken from adults until the authorities have records of everyone's DNA.