Hazel Stewart is to apply to a body that examines suspected miscarriages of justice after losing an appeal against being convicted of murdering her policeman husband.
Lawyers for the former Sunday School teacher confirmed they have been instructed to take the case to the Criminal Cases Review Commission.
The development came after senior judges in Belfast rejected claims that 52-year-old Stewart's previously abandoned challenge to being found guilty of killing Trevor Buchanan should be annulled.
They also ruled there was no merit in all new arguments mounted in a bid to clear her name, including an alleged failure to properly direct the jury on her previous good character.
Lord Justice Gillen said: "The fresh grounds now put before this court are without foundation."
Stewart, who appeared by prison video-link, sat head bowed as her case was comprehensively dismissed in a 40-minute verdict.
She is serving a minimum 18-year jail sentence for the double killing of Constable Buchanan, 32, and 31-year-old Lesley Howell, the wife of her ex-lover Colin Howell.
Both victims were found in a fume-filled garage in Castlerock, Co Londonderry back in May 1991.
Police originally believed they had died in a suicide pact after discovering their partners were having an affair.
Although Howell, 56, eventually pleaded guilty to the murders in 2010 and implicated Stewart in the plot, she has battled to try to have her convictions quashed.
In January 2013 her appeal against being convicted of Lesley Howell's murder was dismissed.
At that stage she dropped her challenge to being found guilty of killing her first husband.
But her lawyers sought permission to resurrect the Buchanan appeal.
They claimed the abandonment should be annulled because she was allegedly not advised by previous legal representatives that it would amount to a dismissal.
It was contended that both Stewart and her husband were told there was no arguable appeal on the Buchanan murder.
Her barrister also set out the grounds on which he argued the conviction should be overturned.
Even though Stewart made admissions in police interviews, the barrister insisted that elsewhere on the tapes she made clear her opposition to Howell's murder plot.
By pleading not guilty and contesting the charges, despite giving no evidence at trial, a full direction on her previous good character should have been given to the jury, the Court of Appeal heard.
Stewart's second husband, retired police superintendent David Stewart, and her children Andrew and Lisa were the public gallery to hear her latest challenge thrown out.
Two of her sisters were beside them to offer their support.
Sitting across from Stewart's family were a sister and three brothers of her murdered first husband.
They listened as Lord Justice Gillen concluded there were no plausible reasons for holding that the abandonment of the appeal should be set aside.
He said she had fully accepted the advice of previous counsel that an appeal for the Buchanan murder was groundless, with all avenues of investigation having been exploredf.
"She knew that the quest was finished," he said.
The decision reached on that point alone was enough to terminate the fresh challenge.
However, the court also rejected contentions that the trial judge failed to properly warn the jury to look for more than just accomplice evidence from Howell of her guilt.
It was further claimed that flaws around the good character direction and advice given on dealing with Stewart's lies during the original police investigation and inquest created a lurking doubt about the safety of the conviction.
But Lord Justice Gillen held that her application must be refused.
He confirmed: "Even if counsel had discussed the current grounds and the applicant had wished the arguments to be put forward (at the original challenge), the outcome would inevitably have been the same, namely that the appeal would have been dismissed."
Following the outcome Stewart was returned to her cell at Hydebank.
Her lawyers had been pressing ahead with separate attempts to have the CCRC refer her conviction for killing Lesley Howell back to the Court of Appeal.
Now, however, they are to add the Buchanan murder to their application.
Solicitor Kevin Winters confirmed: "We are now pursuing this case with the CCRC and have firm instructions to proceed."