Forensic science has been a boon to the criminal justice system. In the past two decades the police DNA database has helped to secure convictions of those who have perpetrated some truly heinous crimes. But the technology's benefits should not be overstated. Fewer than one per cent of all recorded crimes have been solved with the help of the database. And the advances of this technology also raise some difficult questions about privacy and the proper limits of the state.

A person's DNA profile is, by its very nature, personal to them. Once the police or security services have stored someone's DNA they have an indefinite record of that person's very biological identity. There is, thus, a balance to be struck between the collective benefits that flow from the state storing such information and the public's right to keep it private.

It is clear what a proportionate DNA storage system would look like, bearing in mind these tensions. The police would be permitted to retain the DNA of adults convicted of a crime. The price of a person's criminal record would be the forfeiting of this aspect of their privacy. Meanwhile, those who are arrested and subsequently acquitted would have their DNA wiped from the database. And children convicted of a crime should have their DNA records wiped at the age of 18 in order to avoid making them criminal suspects for the rest of their lives. Such a regime would harness the benefits of DNA technology for society, while limiting its impact on individual privacy.

Yet this bears little resemblance to the regime that the Government and the police have set about building in recent years. Under legislation passed in 2004, everyone arrested for a recordable offence is required to submit a DNA sample. And this sample is retained by the police whether or not the individual is subsequently convicted. The result is that DNA profiles of hundreds of thousands of people who have committed no crime are stored on the database alongside those of the guilty.

Last year, the European Court of Human Rights ruled that the retention of the DNA of those with no conviction breached their right to privacy. And so yesterday the Government announced plans to wipe the records of the innocent from the database - but only six years after their arrest. And ministers still intend to retain indefinitely the DNA records of those arrested for terrorist offences, regardless of whether or not they are convicted.

So what we have here is a forced retreat by the Government under pressure from the law. Ministers and the police still refuse to acknowledge that DNA information belongs first and foremost to the private individual and that only in special circumstances should it be appropriated by the state. As far as the Government is concerned, our DNA remains essentially public property. And the general population are not seen as innocent until proven guilty, but as a vast pool of potential suspects.

It would be foolish not to acknowledge that yesterday's proposals represent an improvement. But we should be under no illusions that this move represents a dawning of understanding among ministers over the proper limits of state intrusion into our private lives. Until the DNA database becomes a tightly controlled and ancillary tool in the armoury of the police, rather than the present sprawling and illiberal project, the pressure must continue for it to be cut down to size.