British Army deserter Colin Demet is to give evidence at the inquest for a man who was shot dead by Mr Demet's comrades at a Christmas dance.
Mr Demet will testify before a coroner examining the disputed circumstances of Joseph Parker's death in December 1971.
The 25-year-old married father-of-one was killed when soldiers opened fire at a community centre in Ardoyne in north Belfast during a festive disco.
The episode unfolded when troops entered Toby's Hall, which no longer exists, claiming to be searching for a suspect.
Mr Demet, originally from Manchester, deserted the Army after becoming disillusioned with serving in Northern Ireland during the Troubles, citing incidents such as Mr Parker's shooting and the Bloody Sunday killings in Derry a month later.
He was jailed for his action.
He later wrote a book about his decision to walk out of the Queen's Lancashire Regiment.
Mr Demet is now scheduled to give evidence at Mr Parker's inquest, which starts later this month.
It is understood he was at the scene of the shooting incident, though outside the hall when it unfolded.
A preliminary hearing in Belfast Coroner's Court heard that another soldier who deserted the Army at the same time has been subpoenaed to attend the inquest.
A range of civilian witnesses are also due to give evidence during the two-week hearing.
Today, coroner Joe McCrisken was told that two fresh civilian witnesses had come forward in recent days - one of whom has agreed to testify from his home in Australia.
Mr McCrisken hailed the efforts to trace witnesses for the historic case.
"With very, very limited resources to hold legacy inquests we have, in my view, done a fantastic job in tracking down witnesses and taking statements from witnesses," he said.
The inquest is due to begin hearing evidence on November 13.