The family of Nora Quoirin is to launch a legal challenge to the inquest finding the 15-year-old died by misadventure after she went missing in a Malaysian jungle while on holiday.
A coroner ruled out foul play in the death, finding it to be accidental.
However, her parents believe there is "compelling evidence" she was abducted. They branded the official findings “incomplete”.
The family's legal representatives in the south-east Asian state have confirmed they will be submitting a challenge to the inquest finding "as soon as possible". But could not say when.
"We have not set a target date. Waiting for the notes of evidence from the court," lawyer S Sakthyvell told the Malay Mail.
“There is no fixed time frame under the law for this application. It is to be filed soon as possible."
Nora's family were staying at Dusun eco-resort near Seremban, about 40 miles south of the capital Kuala Lumpur and reported Nora missing the day after they had arrived.
Her disappearance sparked a large-scale search operation. Her naked body was discovered beside a small stream about 1.6 miles from the resort.
Nora was born with holoprosencephaly – a disorder which affects brain development – and her family have said she would not have wandered off on her own.
The teenager had poor motor skills, needed help to walk, and her mental age was about five or six, her parents previously said.
Last week and in an interview with RTE, her mother Meabh who is from Belfast, said: “When we went into the inquest, we had a lot of unanswered questions and while many of those questions cannot be answered we actually found out a great deal about what went on during those 10 days when Nora was missing.
“In fact we felt it really strengthened our case, our belief, that Nora was abducted and we found some compelling evidence to support our view on that.”
She added said: “When we started this we wanted to find out what happened during the ten days in Malaysia but we also of course want justice for Nora and we will continue to fight for that.”