A WA schoolteacher has successfully sued his ex-wife after she lied about him in posts on Facebook.

In a state first, the Bunbury woman was ordered to pay her estranged husband $12,500 after the District Court found she defamed him on the popular social media platform.

In his decision published in December, Judge Michael Bowden said social media defamation had the ability to spread far and wide with the “simple manipulation of computers”.

The offending comments were posted on the mum-of-two’s profile page in December 2012.

“Separated from (husband) after 18 years of suffering domestic violence and abuse. Now fighting the system to keep my children safe,” the post read.

The man’s brother saw the post, took a screenshots and emailed them to him. It was removed in early February 2013.

During the civil trial last year, Judge Bowden was told by several witnesses that when they saw the post, it initially caused them to question the man’s character.

The woman denied writing the post and said it was doctored. She argued she did not know how to use Facebook properly and had it set up for her by another person.

She also defended the post by arguing she had been victim of physical and verbal abuse throughout her marriage to the 54-year-old private school teacher.

Judge Bowden was told the couple were in the middle of a bitter break up involving the Family Court and Department of Child Protection.

He found both spouses had framed evidence to suit themselves during the trial.

However, he said the woman failed to properly prove the domestic violence apart from one incident in 2010.

He also could not accept her explanation for how the Facebook post was created.

“She is simply reconstructing a version of events to try and deny publishing the disputed post which she admitted in written submissions forwarded to the court was seen by her on her Facebook site and which she removed after receiving the concerns notice,” he said.

Judge Bowden said the man had been defamed and deserved compensation.

“Defamatory publications on social media spread easily by the simple manipulation of computers,” he said.

“A public Facebook page is able to be viewed worldwide by whoever clicks on that page and the grapevine effect stemming from the use of this type of medium must be considered.”

In awarding damages of $12,500 Judge Bowden said he had “no doubt” the post had caused the man “personal distress, humiliation and hurt and harm to his reputation.”

“It did cause people to ‘look at him twice’ and be more reserved about their contact with him,” he said.

Interest at six per cent per annum from the date of the post was also ordered.