Witnesses at the murder trial may have perjured themselves according to a 'pre-investigation' file submitted by police

Detectives and prosecutors are examining whether certain witnesses at the Stephen Lawrence murder trial may have perjured themselves while giving evidence, the Crown Prosecution Service has confirmed.

Police passed a file to the CPS last week, though prosecutors say no formal investigation has begun and no arrests have been made. The CPS said: "We have received 'initial papers' from the police in relation to potential perjury allegations during the Lawrence trial. It would be fair to describe this as 'pre-investigation' of these specific matters and we will continue to talk to police about this issue. This is not a file of evidence for our consideration of charges. It is part of ongoing liaison in relation to all issues in this case."

Gary Dobson, 36, told the jury he was at his parents' home at the time of the racist killing in April 1993, while David Norris, 35, could not recall where he had been. The pair are now seeking to appeal against their convictions.

Dobson was given a minimum jail term of 15 years and two months after being found guilty of murder, while Norris must serve at least 14 years and three months.

Police investigations can begin with a "scoping exercise" where the parameters of what will and will not be examined in an inquiry are decided.

The Metropolitan police said: "We continue to work with the CPS on a number of matters, including perjury, as part of our ongoing work following the trial."

The law on perjury dates back to 1911 and states: "If any person lawfully sworn as a witness or as an interpreter in a judicial proceeding willfully makes a statement material in that proceeding, which he knows to be false or does not believe to be true, he shall be guilty of perjury". Just because witnesses in a trial are disbelieved by a jury does not mean they are guilty of perjury, a source added.

The offence carries a maximum sentence of seven years' jail.

In 1998 the Macpherson inquiry into police failings in the Lawrence case considered urging the five prime suspects, including Dobson and Norris, be prosecuted for perjury after their testimony, but eventually decided against it.