Stormont Justice Minister Naomi Long has been urged to reconsider a decision not to call a public inquiry into the case of Arlene Arkinson.
The Co Tyrone schoolgirl went missing in August 1994 after a night out in Donegal.
Her body has never been found, despite extensive searches.
A previous search close to Castlederg for Arlene Arkinson (PA)
Convicted child killer Robert Howard was found responsible, on the balance of probabilities, for the death of the 15-year-old following an inquest in 2021.
He had been out on bail at the time of Miss Arkinson’s disappearance and was the last person seen with the teenager.
Howard, originally from Co Laois, had been charged with her murder in 2002, but acquitted in 2005.
He died in prison custody in England in 2015 while serving a life sentence for the rape and murder of 14-year-old Hannah Williams from London.
Speaking ahead of the 30th anniversary of Miss Arkinson’s disappearance, her sister Kathleen said “the whole system let Arlene down”.
The family’s solicitor, Des Doherty, has urged Ms Long to reconsider the decision not to call a public inquiry.
He said any public inquiry should focus on the activities of Howard “more closely”, but also look at the “legal system in this jurisdiction and how the law and the police behaved in relation to this case and how it was dealt with”.
“If a public inquiry is the only way to keep their case in the public eye, then so be it,” he told the BBC.
Justice Minister Naomi Long said ‘there were not sufficient grounds for a public inquiry’ (Liam McBurney/PA)
“I do not see any other legal option (other than a public inquiry) that is available to the family at this point.
“I think new information will come to light.”
In a statement, Ms Long said she took the decision not to call a public inquiry into the case after concluding there were not sufficient grounds.
“Having met with the Arkinson family, I fully appreciate that the past 30 years have been deeply traumatic as they have continued to grieve and search for answers on behalf of Arlene,” she said.
“My decision not to establish a public inquiry was taken after very careful consideration of everything that had been put before me both verbally and in writing by the Arkinson family and by their legal representative.
“I also took account of the coroner’s detailed inquest findings, the Police Ombudsman report into the handling of the police investigation into Arlene’s disappearance, and the significant changes to police missing person policies.
“In weighing up all of the relevant factors it was my conclusion that there were not sufficient grounds for a public inquiry into this tragic case.”