A man who believes loyalist paramilitaries colluded with security forces in murdering his parents has won High Court permission to challenge alleged state failures to oversee and fund an effective investigation.
Anthony Fox was granted leave to seek a judicial review amid claims he has been let down by a dysfunctional and chronically under-resourced system for probing the killings.
A judge ruled that he has established an arguable case in legal action being taken against the Northern Ireland Office (NIO), Stormont's Department of Justice (DoJ), the PSNI and Coroner's Service.
His parents, Catholic couple Charles and Theresa Fox, aged 63 and 53, were shot dead by an Ulster Volunteer Force gang at their home near Moy, Co Tyrone in September 1992.
The rifle used in their murders has also been linked to at least eight other assassinations in the mid-Ulster area.
Lawyers for Mr Fox described the case as a root and branch challenge to how the system for investigating legacy deaths is allegedly failing victims.
During the hearing it was claimed the NIO and DoJ have provided inadequate resources to investigate deaths in a prompt, independent and effective manner, as required under human rights law.
Probes carried out by the PSNI's Historical Enquiries Team lack sufficient independence and have been undermined by a reliance on out of date ballistic evidence that has now been discredited, according to Mr Fox's legal team.
Police at the time wrongly identified the weapon used in his parents' killings.
The misidentification of the Czech-manufactured rifle only emerged in 2013 during the inquest of another suspected victim of the same mid-Ulster UVF gang.
Pensioner Roseann Mallon, 76, was shot dead as she watched television at a house near Dungannon, Co Tyrone, in May 1994.
The inquest into her murder heard the gun was part of a consignment brought to Northern Ireland by British army agent Brian Nelson.
Mr Justice Maguire was told the Fox family have always believed there was state collusion in the killings.
They are seeking an order compelling the authorities to properly fund and carry out an effective investigation.
In a ruling communicated to legal representatives, the judge concluded that leave to apply for judicial review should be granted.
He said: "The court is of the view that an arguable case has been disclosed by the applicant."
A date for full hearing of the case may now be fixed at a review next month.
Mr Fox's solicitor welcomed confirmation that the challenge has cleared the first hurdle.
Paul Pierce, of KRW Law, said: "This enables our client to move forward towards a hearing which will allow the court to examine the systemic failures which lie at the heart of a chronically under-funded system."