A "belt and braces" approach is being adopted to ensure a former top detective appears at the inquest for missing teenager Arlene Arkinson, a coroner's court has heard.
Eric Anderson, a retired detective superintendent, may still have documents relating to the investigation into the schoolgirl's disappearance more than 20 years ago, it was claimed.
Coroner Brian Sherrard told a preliminary hearing at Laganside court complex: "There has been a suggestion that Mr Anderson may hold papers.
"They may be the same as we have, who knows, or he may no longer have papers."
Mr Anderson has cited ill health as a reason for non-attendance at other high-profile inquests.
However the coroner has demanded that he bring any relevant information to a preliminary hearing scheduled for later this month.
If the ex-Royal Ulster Constabulary (RUC) officer refuses to co-operate, a formal summons will be issued, the court was told.
Mr Sherrard added: "This is a belt and braces approach.
"I assume Mr Anderson will co-operate but as a precaution he will also be formally summonsed."
Arlene, 15, from Castlederg, Co Tyrone, vanished after a night out at a disco across the Irish border in Co Donegal in 1994.
She was last seen with convicted child killer Robert Howard, who died in prison last year.
Howard was acquitted of the teenager's murder by a jury that was unaware of his previous conviction for murdering a schoolgirl in south London.
The 71-year-old was always the police's primary suspect in Arlene's disappearance and had been set to give evidence before the inquest due to start on February 1.
In eight years of preliminary proceedings, a number of start dates were missed because of police delays in disclosing documents and issues around security vetting.
Some eight outstanding files are now ready to be handed over to lawyers for the Arkinson family, with other social services documents due to be disclosed next week, a barrister representing the Police Service of Northern Ireland said.
Applications to have the identities of some witnesses protected are also well advanced and are awaiting formal approval from the Secretary of State.
Kevin Rooney said: "Tranche one is all but done and has passed the chief constable stage and should be with the minister for a ruling."
The inquest is being heard without a jury and could last for several months - with proceedings streamed to Omagh court house to facilitate the missing teenager's family.
Afterwards, Kathleen Arkinson said she looked forward to seeing Mr Anderson in court and hoped for an apology over the police handling of the case.
Ms Arkinson said: "I can't wait to see Eric Anderson in court. He owes my family an apology. He has no right to have any papers, if he has them, on Arlene or anybody else.
"I want him to apologise for the way my family was treated by the police."
At one stage officers dug up the back garden of her home, near Castlederg, she said.
Meanwhile, Ms Arkinson has also appealed for anyone who may have information about her sister's disappearance to come forward.
"We have only a few weeks left before the start of the inquest and if anybody knows anything, anything at all, I want them to come forward to the police or to their reverend or whoever - no matter how small they think it is - it could be significant to us."