An important witness has not been interviewed by Irish police investigating the murder of Sinn Fein spy Denis Donaldson, an inquest has been told.
Mr Donaldson was shot dead more than six years ago by gunmen in a rural cottage near Glenties, Co Donegal. The Real IRA claimed it was responsible.
The former senior Sinn Fein official had confessed to spying for police Special Branch and secret service MI5 just months before he was killed.
Senior police told an inquest in Letterkenny, Co Donegal, that a file had been submitted to the Director of Public Prosecutions (DPP) and they anticipated a decision on whether to pursue the criminal case within four months.
Fiona Doherty, a barrister for the family, told the inquest: "The family does welcome the fact that a file has been submitted, if only because it means there has been some progress in the case. However, the family have had ongoing contact with the gardai about the progress of the investigation and they are concerned about the manner in which the investigation has been carried out.
"There has been one witness in particular that they know has not been spoken to by the Garda, a witness they regard as very, very important."
Lawyer for the police Stephen Byrne said it had been a good investigation. Donegal coroner Denis McCauley has opened the inquest into Mr Donaldson's death 10 times and each time it has been adjourned.
The sequence of events surrounding his death dated back to 2002 after three men including Mr Donaldson were arrested following a raid on Sinn Fein's Stormont office. The power-sharing executive between unionists and nationalists collapsed and Government restored direct rule to Northern Ireland a week later.
In 2005 charges against three men were dropped and within days Sinn Fein said Mr Donaldson was a British agent and expelled him from the party. He later said he had worked as a spy since the 1980s. In April 2006 Mr Donaldson was found shot dead in the remote Glenties area of Donegal.
The coroner welcomed the fact that police had submitted a file to the DPP and said if a decision was not made to hold a criminal trial, he hoped to have the inquest under way next year. The case was adjourned to March 21 next year.