A judge is to decide next week whether he will step aside from a case over a report into the Loughinisland murders.
Mr Justice McCloskey had been due to announce whether he would quash a report into the 1994 murders.
However, he has been asked to withdraw from the case over a possible perception of bias.
Last month, he ruled that the police ombudsman's finding of collusion between some officers and the killers was "unsustainable in law".
The judge ruled in favour of two ex-police officers who brought the case.
Six Catholic men were shot dead as they watched a football match in the County Down village on 18 June 1994.
Lawyers for the police ombudsman and families of the victims have lodged submissions asking the judge to step aside because he had previously represented one of the officers in a different case.
Six men died at Loughinisland when loyalist gunmen burst into the Heights Bar and opened fire as they were watching the Republic of Ireland play Italy in the World Cup.
The victims were Adrian Rogan, 34, Malcolm Jenkinson, 53, Barney Green, 87, Daniel McCreanor 59, Patrick O'Hare, 35, and Eamon Byrne, 39. Five others were wounded.
No-one has ever been convicted over the attack.
In June 2016, the police ombudsman found there had been collusion between some police officers and the UVF gunmen.
Two police officers challenged the legal basis of the report and Mr Justice McCloskey had been due to announce last week if he would quash part or all of its findings.
In 2001, when he was a barrister, Bernard McCloskey QC, was involved in an unsuccessful challenge to a report by former Ombudsman Nuala O'Loan which found there had been failings by the RUC during the investigation into the 1998 Omagh bombing.
Guidelines issued to judges by the lord chief justice state: "Past professional association with a party as a client need not in itself be a reason for disqualification, but the judge must assess whether the particular circumstances, and in particular any prior knowledge relevant to the case, could create an appearance of bias."
Relatives of the Loughinisland victims want a new judge to be appointed to adjudicate on the challenge to the Loughinisland report.
The submission contends that Mr Justice McCloskey's involvement in the 2001 case creates the potential for a public perception of unconscious bias.
A lawyer for the ombudsman is believed to have lodged a similar submission.
The judge will announce his decision next week.