Nicola Stocker, 51, of Longwick in Buckinghamshire, made remarks about Ronald Stocker in an online exchange with his new partner, Deborah Bligh, in December 2012.
Mr Stocker, 68, of Aston Clinton in Buckinghamshire, had won a court battle against his ex-wife at London’s High Court after Mr Justice Mitting found those reading the comments would think she meant he had “tried to kill” her – a ruling that was upheld by the Court of Appeal.
Overturning the earlier decisions, a panel of five Supreme Court justices concluded Mr Justice Mitting made a legal error by relying on the dictionary definition of “strangle” when he found her post meant her ex-husband had “tried to kill” her.
Giving the lead ruling in London today, Lord Kerr said: “In consequence, he failed to conduct a realistic exploration of how the ordinary reader of the post would have understood it.
“Readers of Facebook posts do not subject them to close analysis. They do not have someone by their side pointing out the meanings that might, theoretically, be given to the post.
“In view of the judge’s error of law, his decision as to the meaning of the Facebook post cannot stand.”
Lord Kerr said the “ordinary reader”, knowing Mrs Stocker was still alive, would “unquestionably” have interpreted the post as meaning Mr Stocker had grasped her by the throat rather than deliberately tried to kill her.
During the High Court trial in 2016, the court heard the allegations were published to 21 individuals who had authorised access to the page.
They were also visible to 110 of Ms Bligh’s “friends” and to their Facebook “friends”.
Ruling in Mrs Stocker’s favour and ordering Mr Stocker to pay all legal costs, Lord Kerr said: “It is beyond dispute that Mr Stocker grasped his wife by the throat so tightly as to leave red marks on her neck visible to police officers two hours after the attack on her took place.
“It is not disputed that he breached a non-molestation order. Nor has it been asserted that he did not utter threats to Mrs Stocker.
“Many would consider these to be sufficient to establish that he was a dangerous and disreputable man.”
The justices found Mrs Stocker’s defence of justification in the libel action should not fail.