The blanket ban applies irrespective of the age of the person or findings of innocence by the courts

Richard Gordon QC

Mr Marper, who has no previous convictions, was arrested and charged with harassment of his partner in March 2001.

A trial never took place because his partner decided not to press charges, and subsequent letters confirmed the couple were back together again.

Mr Gordon said South Yorkshire Police refused requests to destroy the DNA samples and prints taken from both, claiming a change in the law allowed them to retain them "to aid crime investigation".

The QC accused the force's chief constable of operating an unlawful blanket policy of retaining all samples and prints, save in undefined exceptional circumstances.

'Disproportionate'

Mr Gordon told the court it was not the intention of Parliament that innocent people caught up in the criminal justice system "should have aspects of their identity retained and used by police for ever and a day".

The DNA database at the Forensic Science Service laboratory

Lord Justice Rose, sitting with Mr Justice Leveson, was told: "The blanket ban applies irrespective of the age of the person or findings of innocence by the court."

Mr Gordon said the practice was unjustifiable in both his clients' cases and "not necessary in a democratic society for the prevention of crime".

David Bean QC, appearing for the Chief Constable, said keeping the profiles was plainly justified and in the interest of public safety, prevention of crime and the protection of the rights and freedoms of others.

Rabinder Singh, for Home Secretary David Blunkett, said the minister agreed there was no incompatibility with the human rights convention.

The court reserved judgment, which will be given in the near future.

'Appalling practice'

More than 750,000 DNA profiles are now held on the �187m database and the target is to have the profiles of each of Britain's three million active criminals stored by April 2004.

Home Office figures show that every week around 1,600 DNA matches are made either connecting a suspect to a crime scene or linking crime scenes together.

Police see the resource as a valuable asset in the fight against crime.

But critics, including human rights group Liberty, have criticised the "appalling" practice of keeping samples from people who have not been convicted.

Scientists have warned the larger the DNA database gets the greater the chance of finding two samples that look the same but are not actually from the same person.