“Press freedom is the most fundamental freedom in modern society because it protects all the other freedoms,” he said.
“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.”
Police are investigating how information contained in a Police Ombudsman for Northern Ireland document appeared in No Stone Unturned.
Police Service of Northern Ireland chief constable George Hamilton, citing a potential conflict of interest, asked Durham Constabulary to take on the probe in the wake of the film’s release.
No one has ever been convicted of the Loughinisland murders.
In a 2016 report, Ombudsman Dr Michael Maguire concluded the security forces colluded with the UVF killers.
Mr Birney and Mr McCaffrey have insisted the document was leaked anonymously and have criticised the police characterisation of it as a “theft”.
They have questioned why investigative resources are being diverted to their film when the Loughinisland killers have not been caught.
Opening the Fine Point Films case on Tuesday morning, Barry Macdonald QC said police seized millions of documents.