Damilola moved to England from Nigeria

Detective Chief Superintendent Tony Crofts wants such witnesses to be questioned only by the judge or a mediator, to avoid them jeopardising the prosecution case.

The case against the four youths accused of Damilola's murder failed largely because the main prosecution witness - a 12 year old girl known as 'Bromley' - was undermined during relentless cross examination by defence barristers.

But the proposals have been criticised by child law specialist, Allan Levy QC, who said they were impractical, and a way for prosecutors to "offload" their responsibilities.

"Our Crown Prosecution Service and indeed senior police officers should be able to - and most are able to - assess witnesses, and should only put forward witnesses who are reliable and truthful," he said.

I would prefer a situation where the judge would call a witness and direct how that witness is dealt with Det Chief Supt Crofts Metropolitan Police Old adversaries meet again Transcript: Bromley interview

He told BBC News 24 he did not want to move away from the UK's adversarial justice system, where juries make decisions based on opposing arguments.

Mr Crofts also called for judges to have the option to be more open with the court, including jurors, about any "misgivings" there are about the reliability of the witnesses' evidence.

And he said lawyers and judges needed more training in dealing with such witnesses, who were termed by academics and sociologists as the "underclass".

"This is a group that is often very young and very vulnerable due to cultural, educational and sociological background and lives on the periphery of our society," he told Radio 4's Today programme.

'Drip fed' information

"We should put them in a special category. They are extraordinarily vulnerable, because they appear on the surface - as she (Bromley) does - to be very challenging, rude, hard, streetwise, mature beyond their years, but they do not actually understand or act in a way that society recognises."

He said in cases such as Bromley's, witnesses "drip fed" information to police officers, making a series of revelations over time, which cast doubt over their reliability.

Liberal Democrat spokesman for home affairs, Simon Hughes, told Today he would not dismiss Crofts' suggestion out of hand.

My mind does not run like an adult Witness Bromley Witness Bromley on her experience in court

"But we need to be careful - in this case it may have been that however this witness had been examined, they would not have been able to get safe evidence," he said.

Bromley told the court she saw the murder of Damilola. He bled to death in a stairwell in Peckham, south London, in November 2000, after being stabbed with a bottle.

But Bromley was highly temperamental in giving evidence and was dismissed by the judge as unreliable.

He said police in the Damilola case were hampered by the fact that witnesses were more likely to be from deprived homes.

"You are highly unlikely to find good witnesses. You are going to find people who are damaged, they are from these sub-strata of society and we do sometimes have reservations about their evidence," he said.

He admitted police were unsure whether Bromley really saw Damilola being stabbed.

'Outcry'

"But what could we, the police do? If she hadn't been called by the prosecution there would have been an outcry about the fact that we had ignored the evidence of a supposed eye-witness."

He said witnesses were either cast as honest or as liars, with undue attention to the "massive grey area", where police are unsure what to believe.

Investigations into Damilola's murder were continuing, but there was little hope of a conviction, he added.

The witness tells BBC Radio 4's It's My Story: The Witness, that her life was ruined by the experience of the trial and the fear of retribution.

She said she had tried to commit suicide by jumping under a bus after her testimony was rejected.

• It's My Story is on Radio 4, Thursday 7 August, at 2000 BST