Lawyers for the family of a man shot dead in Derry on Bloody Sunday are challenging a decision not to name a former British soldier charged with his murder.
They say there is no legal basis for not identifying the man referred to as Soldier F.
Relatives of those killed in January 1972 have described the decision to prosecute the former British paratrooper as historic.
He is charged with murdering James Wray and William McKinney, and five attempted murders.
The case was back at Derry Magistrates Court today for a brief hearing, before being adjourned until January.
Soldier F was not there in person, and unlike virtually all other defendants facing murder charges, he cannot been named.
That is because of an interim court order granting him anonymity.
Lawyers for the family of William McKinney and four of those wounded on Bloody Sunday have written to the Public Prosecution Service to challenge that decision.
They have asked for an explanation of the legal basis for the decision. "Providing this former soldier with anonymity marks a very, very serious departure from accepted norms and principles of open justice," solicitor Ciarán Shiels said.
"The position of the families and the wounded is that he should not be receiving more favourable treatment than other defendants before the courts.
"We believe it is going to be very, very difficult for the PPS and the courts to stand over the current position."
In the letter to the PPS, the lawyers point out that the former soldier gave evidence in public to the Bloody Sunday inquiry in Derry’s Guildhall in 2003.
They say his name has been known to the families of the Bloody Sunday victims for the past 20 years, and point out that nothing has happened to him during that time.
In a statement, the PPS said the correspondence is under consideration.
The lawyers say that if the PPS refuses to lift the restriction on identifying Soldier F, they will launch legal action in an attempt to force it to do so.