Former Northern Territory youth detainee Dylan Voller has secured a win against three of Australia's largest media organisations in a defamation case involving Facebook posts by members of the public.

Key points: Dylan Voller's defamation case centres around media coverage posted on Facebook

Dylan Voller's defamation case centres around media coverage posted on Facebook The judge found that the organisations could have chosen to monitor or hide the comments

The judge found that the organisations could have chosen to monitor or hide the comments The court is yet to rule on whether the material contained in the comments was defamatory

Mr Voller brought a civil case against Fairfax Media, Nationwide News and Sky News over comments posted in reply to articles placed on the social media platform between July 2016 and June 2017.

The posts were made on the Facebook pages of the Sydney Morning Herald, The Australian, Sky News, The Bolt Report and The Centralian Advocate.

In his statement of claim Mr Voller — whose case of mistreatment at the Don Dale Youth Detention Centre sparked a royal commission — said the defendants should have known there was a "significant risk of defamatory observations" after placing the articles online.

He said the organisations could have chosen to monitor or hide the comments.

Supreme Court Justice Stephen Rothman ruled the media organisations could be considered publishers of the third-party comments and were therefore liable for them.

"Each defendant was not merely a conduit of the comment," he said in his judgment.

"[They] provided the forum for its publication and encouraged, for its own commercial purposes, the publication of comments."

The court has not yet ruled on whether the material contained in the comments was defamatory.

"A defendant cannot escape the likely consequences of its action by turning a blind eye to it," Justice Rothman said.

Monitoring 'not sufficient'

Among the allegedly defamatory imputations were that Mr Voller had "brutally bashed a Salvation Army officer", that he beat and raped an elderly woman, that he had committed a carjacking and had bitten off someone's ear.

Mr Voller said he had "been subjected to hatred, ridicule and contempt" and had "suffered and continues to suffer distress and damage to his reputation".

The court considered an expert report from Ryan Shelley, who manages a social media and digital marketing agency, about the methods by which media organisations can moderate comments.

Mr Shelley said occasional monitoring of comments was not sufficient, "particularly for media outlets of significant size and with significant available resources".

"Strategies could have been put in place to allow for a more robust and deliberate attempt at monitoring comments," Mr Shelley wrote in his report, tendered to the court.

Mr Voller's case of mistreatment while at the Don Dale youth Detention Centre was documented in an episode of the ABC TV program Four Corners in 2016.

Within 36 hours, a royal commission into youth detention centres was called by then-Prime Minister Malcolm Turnbull.