Everyone knows who killed Stephen Lawrence. It was a gang of vile thugs, two of whom were convicted of murder yesterday, on the basis of forensic evidence. Everyone thinks they know who the other thugs were in what the criminal law rightly classes as a "joint enterprise". Many even know them by name and would recognise their photographs. It surely can only be a matter of time before the other ones are prosecuted and convicted.

But what do we actually know? As it stands there appears to be no forensic evidence linking any of the other individuals to the horrific crime of Stephen Lawrence's murder. There is also no eye witness evidence which can be put before a court. As the Court of Appeal pointed out [2] regarding the original prosecution when quashing the acquittal of Gary Dobson so that he could again stand trial:

Following their arrests, Knight and Neil Acourt were charged with the murder of Stephen Lawrence, after each of them was identified on identification parades by Duwayne Brooks as part of the attacking group of white youths. However the reliability of these identifications was called into serious question. On any view Brooks had found himself in a frightening situation, with only a brief opportunity for making a correct identification at night, under artificial light, in a desperately fast-moving incident.

Moreover, after he had identified Knight, he himself confirmed to an independent police officer that he had not actually seen the faces of any of the attacking group, but had been given a description of them before he took part in the parades. Accordingly, the prosecution of Knight and Neil Acourt was discontinued.

As to Dobson, he was never identified by anyone. [...]

The evidence of Brooks was crucial to the success of the prosecution, but as we have indicated, it was flawed. The question whether his evidence should be placed before the jury was examined in detail at a voir dire. Brooks gave evidence on three days. After hearing argument, Curtis J concluded that his evidence of identification of any of those involved in the attack on Stephen Lawrence was inadmissible. The judgment was impeccable, the reasoning clear, and the conclusion unavoidable.

And so we have a gap. On one hand, there are three alleged murderers who many sensible and informed people believe with complete certainty were part of the gang which attacked Lawrence. On the other hand, there seems -- at least currently -- to be no available evidence to warrant any prosecution, let alone convictions beyond reasonable doubt.

This is the sort of situation which usually cannot hold. If the matter cannot be tried in a court of law, then it seems it will be tried in the so-called court of popular opinion. But the problem with those who "everybody knows" are guilty is that they sometimes are not, at least not of the crime being alleged. Many miscarriages of justice and media sensations have been on the misconceived basis that they "must" be guilty. Examples do not even have to be listed; we all know them.

Unless there is new evidence -- possibly either in forensic form or a confession by one of the two now convicted murderers -- then the dreadful situation will persist of there not being any further prosecution of the others widely suspected of killing Lawrence. No tabloid campaign or new judicial inquiry can change this stark fact.

Had the police conducted a competent initial murder inquiry in the days after Lawrence's murder, there would perhaps be other evidence. But for whatever bad reason the police did not do so. Such helpful evidence cannot now be contrived, and there cannot be any prosecution without evidence. Mere certainty, however well-grounded and widespread, is not enough. The Crown has to prove guilt beyond reasonable doubt, and popular opinion is not admissible in court.

So what should happen to those suspected of murder, but still at large? Should there be no adverse comments? No negative publicity? Should everyone just hold their tongue? Well, without the prospect of proceedings, there is no "due process" to be respected, as there is no determination of guilt in the offing. In that way, there is no legalistic objection to popular opprobrium. It is not sub judice.

However, one day there could be new evidence. There may be a further advance in forensic science which would affect this case. Or there could be a confession implicating another. In those circumstances, there would need to be "due process" with the innocence being presumed until guilt is proved. But would that now be really possible? There is no doubt that the defence lawyers of those prosecuted would contend a fair trial would not now be possible; but, as the Court of Appeal showed when quashing Dobson's acquittal, the courts can be robust in saying that trials should go ahead even when there has been bad publicity. But this robustness is not inevitable.

It may be important that we can join the clamour of condemning those who look as if they have evaded justice. Unfortunately, that same clamour can also be exploited to help the culprit escape justice. Accordingly, even when not legally required for a current legal case, the presumption of innocence until proven guilty remains a sensible policy. Those seeking to escape justice really do not need any further help to get away with it.

David Allen Green is legal correspondent of the New Statesman