Leading article: A case that still casts a long shadow over Britain

Britain still continues to feel the shock waves emanating from the savage murder of a promising black student over 13 years ago. The parents of Stephen Lawrence suspected from the very first that police racism and corruption were behind the shocking inability of the authorities to build a proper case against the five white men accused of murdering their son in an unprovoked racist attack. They found partial vindication in the Macpherson report of 1999, which condemned the police for "institutional racism". But though Macpherson discovered inept detective work, it could not detect outright corruption in this particular case.

Yet now evidence has come to light that strongly suggests the police were indeed corrupt in their handling of this investigation - and that the Lawrence family were right all along. A BBC1 documentary last night screened testimony from Neil Putnam, a former detective, claiming that a key officer on the Lawrence case was in the pay of a south London gangster, who also happened to be the father of one of the prime suspects. This is the sort of squalid collusion between criminals and police that one assumes was stamped out long ago. Not so, it seems. Putnam's character may not be unimpeachable. He was convicted of corruption himself. But his evidence has been used to convict a number of other corrupt officers. The programme also cast doubt on the alibis of the five accused. Put together, it is a compelling package of evidence.

It is true that John Davidson, the officer who stands accused of accepting bribes, who has since retired to Minorca on a police pension, has been cleared by a corruption investigation by the Metropolitan police. But this took place in the days before the post-Macpherson reforms had taken effect - and before the establishment of the Independent Police Complaints Commission. We can hardly be expected to put our faith in the comprehensiveness of this inquiry, especially in the light of all that has emerged since then. It is striking that even the Deputy Assistant Commissioner of the Metropolitan police, John Yates, who is in charge of crime reinvestigation, has told the BBC that he believes Davidson is corrupt. The Independent Police Complaints Commission is duly gearing up for a fresh investigation.

For this, the BBC deserves full credit. The Corporation has proved that documentary journalism, a format that is struggling to survive in an increasingly commercialised televisual world, can still play an important role in public service broadcasting. It also deserves credit for recognising that significant questions still hang over the Lawrence case. The Macpherson inquiry's findings launched a national debate about racism, not just in the police but in almost every aspect of our national life. In the end the words "Stephen Lawrence" came to symbolise a good deal more than the cruel murder of one black student. The case, and everything associated with it, became a battleground for the soul of Britain. But the BBC's journalism has concentrated our minds wonderfully once again on the scandal at the very heart of the matter: the failure of the criminal justice system to prosecute successfully those responsible for the murder. Despite three police investigations no one has been convicted. This failure continues to tarnish the reputation of the Metropolitan police and British justice.

At the very least, there must be a reinvestigation of Davidson and the Metropolitan police for corruption. And we must hope that this new evidence will also provide justice for the dignified parents of Stephen Lawrence. For the only way this case can be laid to rest is through the conviction of those who murdered their son on the streets of south-east London all those years ago.