A police state-style arrest operation was launched against two journalists after confidential material was aired in a documentary, a barrister has said.
A vast amount of unrelated research, including millions of pages of documents, was taken when officers raided offices and the homes of award-winning film-makers Trevor Birney and Barry McCaffrey, their lawyers said.
The pair were detained last year over the alleged theft of a police watchdog document that appeared in their film No Stone Unturned, about the murders of six men in Loughinisland, Co Down, in 1994.
They remain under police investigation and are on bail.
Conservative MP and former Brexit secretary David Davis was among those supporting the investigative duo and said the case should be highlighted around the world.
Opening a legal case in Belfast on Tuesday morning, Barry Macdonald QC said: “This was the kind of operation more associated with a police state than with a liberal democracy that does have in place laws designed to protect investigative journalists and their sources from this kind of intrusion.
“This application arises from a police search operation that was nothing less than outrageous.
“Police raided business premises of two journalists and a film company, rifled through their files, accessed millions of documents and seized computers, phones and documents.”
The 2017 film broke new ground by naming suspects it said were involved in the Ulster Volunteer Force (UVF) killings of six Catholic men gathered in a village pub watching the Republic of Ireland play a World Cup football match on TV.
Mr Birney and Mr McCaffrey are taking a judicial review against the execution of a police search warrant related to the programme.
Mr Macdonald said: “This operation sets off alarm bells and flashing blue lights amongst media organisations.
“It set off alarm bells because of the grave implications for freedom of the press.”
Journalistic documents, computers, notebooks, files and digital material seized by police when they searched the Fine Point film production company were bagged and sealed.
Officers are investigating how information contained in a Police Ombudsman for Northern Ireland (PONI) document appeared in No Stone Unturned.
Police Service of Northern Ireland (PSNI) Chief Constable George Hamilton, citing a potential conflict of interest, asked Durham Constabulary to take on the probe following the film’s release.
Barrister for the police Peter Coll QC said officers did not have to prove a theft had taken place when deciding to launch the operation, but only to harbour suspicions.
He said the information in question surrounded the identity of suspects and those who have provided information to police and came from either a Crown servant or government contractor.
Mr Coll added: “That information would have been such that the person providing it to PONI would have had a wholly reasonable expectation that it would be provided, entrusted, on the basis of confidence.”
No one has been convicted of the Loughinisland murders.
In a 2016 report, ombudsman Dr Michael Maguire concluded the security forces colluded with the UVF killers.
Officers appeared to search every desk in the journalists’ office and take material unrelated to Loughinisland, including one surrounding alleged clerical child sex abuse, Mr Macdonald told the Court of Appeal in Belfast.
He said the judge who granted the search warrant did not have issues surrounding the protection of journalistic sources properly in mind.
“The judge effectively unfortunately allowed himself to be used by a single-minded police officer who had his own agenda.”
Outside court, Mr Davis said press freedom was the most fundamental freedom in modern society because it protected all the other freedoms.
“Protecting press freedom is not just about protecting journalists, it is about protecting their whistleblowers and their witnesses, it is about protecting the ability to expose wrongdoing and expose failure, and that is what these journalists are doing, and they don’t deserve to go through what they are going through now.
“Their cause is so important it should be known throughout the whole of the UK and the rest of the world.”