A former member of the UDA, who is charged with the murder of Human Rights solicitor, Pat Finucane, in 1989, claims that the RUC knew about the plot before it occurred.
William Stoby supplied the gun used to kill Mr Finucane and was an informer for the special branch of the RUC at the time.
He claims that he warned the police after he handed over the gun, but that no action was taken.
The trial is expected to collapse after the main witness for the prosecution withdrew his evidence, allowing Mr Stoby to walk free.
He has now joined the Finucane family’s call for an investigation into the links between the RUC and Loyalist paramilitary groups.
Mr Stoby also claims that the RUC Special Branch tried to kill him before he could reveal his accusations. He was shot six times, but managed to survive.