Sir William Macpherson has proposed that people acquitted of crimes should be liable to re-trial if compelling new evidence arises.

The Home Secretary, Jack Straw, told the House of Commons that he would ask the Law Commission to consider the proposal.

Three of the five suspects in the Lawrence case were acquitted of Stephen's murder. The law does not allow them to be tried a second time, and even if the Law Commission agrees with the proposal, the change would not be retrospective.

Just one go

According to the ancient doctrine of double jeopardy, prosecutors have just one go at proving the case against somebody, and this applies even where - as with the Lawrence case - it has been a private prosecution.

For the accused person, it means once defendants have been found not guilty - which includes cases where the prosecution has simply not been able to prove their guilt - then that is an end to the matter.

They can rest assured that they will not find yourself in court having to answer the charges again.

Benefit of doubt

Like the right to silence, the presumption that everybody is innocent until proven guilty, and the requirement for charges to be proved "beyond reasonable doubt", double jeopardy is part of the legal culture which firmly puts the onus of proving cases onto the prosecutors.

Three years ago there was a slight relaxation of the double jeopardy rule for cases where people had been found not guilty but where there had been so-called "jury nobbling".

But any further relaxation in the rule is likely to be vehemently opposed by civil liberties groups and lawyers alike, particularly since the right to silence has been restricted.

For liberal campaigners anxious to see reform after Stephen Lawrence's death, the proposal could cause a clash of interests, for the rule is seen as a bulwark of defendants' rights.

Wider perspective

Clare Connelly, lecturer in law at Glasgow University, said many people would naturally be calling for reform after the Lawrence case.

But she added: "You really have to take a wider perspective. The process of law really cannot be based on the individual circumstances of one case, because then you lose all the objectivity that is required.

"The difficulty if you remove the doctrine is that you would remove the protection from the accused," she said.

"The focus of this case is a botched job by various criminal enforcement agencies, which has caused a lot of frustration.

"But I don't think that situation is the norm. It's probably more normal that we would have to protect accused people from victimisation and recurring prosecution."

With all the state's resources at the prosecution's disposal, it was incumbent on the prosecution to get its case right first time, she said.

"There's a huge onus if they are going to bring a case to have it properly prepared."

If the law were changed, she said, it might lead to the state having unending powers to prosecute.