Prosecuting lawyers and barristers will be allowed to interview their witnesses before the start of a trial to assess the reliability of their evidence.
Interviews will be recorded and made available to the defence
Attorney General Baroness Scotland will announce that a pilot scheme is to be rolled out across England and Wales.
The proposal came up after four youths were cleared in 2002 of murdering south London schoolboy Damilola Taylor.
The judge ruled the evidence of the main prosecution witness, a 12-year-old girl, could not be relied on.
Evidence and character
The pilot scheme was set up in Greater Manchester, Merseyside, Lancashire and Cumbria.
Under the initiative, prosecutors could ask witnesses about their evidence and their character before cases came to court to assess their reliability.
Baroness Scotland will announce on the seventh anniversary of Damilola's death that the scheme will be extended.
Interviews will be recorded and made available to the defence to make sure prosecutors do not coach witnesses or help them improve their performance in court.
Defence lawyers are already to able to question their clients and witnesses but since the 19th Century there has been a ban on prosecutors doing the same before court cases.
In 2006 after three trials, brothers Danny and Rickie Preddie, aged 18 and 19, of Peckham, south London, were found guilty of the manslaughter of Damilola.