BBC legal affairs correspondent Jon Silverman outlines the law and its implications.

If the law on double jeopardy was reformed, the case of Billy Dunlop might be re-examined.

Dunlop, from Billingham on Teesside, was twice tried and on the second occasion acquitted, of murdering a pizza delivery girl, Julie Hogg.

Ms Hogg went missing in November 1989 and her body was discovered behind a bath panel in February the following year.

Nine years after his two trials in 1991, Dunlop faced a court again - this time on a charge of perjury.

He confessed to the murder and was jailed for six years.

As the law stands, he cannot be re-tried for murder.

But if Law Commission recommendations are implemented, the confession would almost certainly count as new evidence and could form the basis for a re-trial.

Gangland killings

Another case is that of the notorious East End gangster, Freddie Foreman, who has escaped prosecution after admitting on television that he had committed two murders for the Kray twins, Reggie and Ronnie.

Foreman was acquitted of the murders of Frank " Mad Axeman " Mitchell and Tommy " Ginger " Marks in the 1960s.

Whether a fresh prosecution of Foreman, now 68, would be considered in the interests of justice is debatable.

A change in the double jeopardy law would certainly result in pressure for a re-examination of a case which created public shock last year.

Michael Weir was convicted of murdering 79-year-old Leonard Harris in North London.

DNA evidence

The crucial evidence was blood found on his gloves and subjected to DNA analysis.

This showed a match with a sample of Weir's blood taken in connection with drugs offences a year earlier.

The Court of Appeal ruled that this was a breach of the Police and Criminal Evidence Act and should have been ruled inadmissible.