Blakelock killing: Why did case fail again?
9 April 2014 Last updated at 23:06 BST
A man has been acquitted of the murder of PC Keith Blakelock - raising questions about why the case was ever brought to court.
On Wednesday Nicholas Jacobs was found not guilty of killing the police officer during the Blackwater Farm riots in north London in 1985.
It is the latest case to fail. In 1987 three men were found guilty of the murder, but were freed on appeal four years later.
Mark Easton reports.