The national DNA database is the largest in the world
Keeping DNA samples of innocent people breaches their human rights, a court has been told.
Two British men have brought a case to the European Court of Human Rights in Strasbourg to try to get their DNA removed from the UK national database.
The men, both from Sheffield, were arrested and had DNA lawfully sampled but were later cleared of any offence.
A ruling is expected later this year, and if successful could mean hundreds of thousands of samples being removed.
Lawyers for the men told the court that retaining DNA samples casts suspicion on people who have been acquitted of crimes or had their cases dropped.
They said they should be treated the same as people who have not been under suspicion, and therefore do not have to have their DNA and fingerprint samples on record.
Keeping such records of innocent people breached "respect for private life" and "prohibition of discrimination" aspects of the Human Rights Convention, the lawyers added.
The Home Office has acknowledged the current DNA database of 4.5 million samples in England and Wales could be affected by the case.
DNA proved vital in the recent high-profile cases of Steve Wright, who murdered five women in Suffolk, and Mark Dixie, murderer of Sally Anne Bowman.
They were both caught after their DNA had been taken in connection with unrelated offences.
One of the men seeking the ruling in Strasbourg, Michael Marper, 45, was arrested in 2001.
He was charged with harassing his partner but the case was later dropped after the couple were reconciled.
The other man - a teenager identified as "S" - was arrested and charged with attempted robbery but was later acquitted.
In both cases the police refused to destroy fingerprints and DNA samples taken when the men were taken in to custody.
The men went to the European Court of Human Rights after their cases were thrown out by the House of Lords.
All DNA samples taken during criminal inquiries in England and Wales are retained, but most are destroyed in Scotland if the person is not charged or convicted.