For five years, the serious harm element in s 10A has been applied, argued and dissected almost entirely at first instance. That changed on 10 June 2026, when the Full Court of the Federal Court — Colvin, Wheelahan and Abraham JJ — handed down Latham v Greenwich [2026] FCAFC 82, dismissing both Mr Latham’s appeal and Mr Greenwich’s cross-appeal from the decision of O’Callaghan J in Greenwich v Latham [2024] FCA 1050.
The result: the finding that Mr Latham defamed Mr Greenwich in a single post on X (formerly Twitter), and the award of $140,000 in damages including aggravated damages, both stand. But the decision’s significance runs far beyond the parties.
The First Real Appellate Word on s 10A
The judgment is widely regarded as the most comprehensive appellate treatment to date of the serious harm element introduced by the 2020–21 reform package. Until now, trial judges applying s 10A have worked largely from first-instance authority and English guidance under the equivalent provision. Latham v Greenwich gives Australian courts binding appellate guidance on how the element is to be approached and proved — guidance that every serious harm argument from here on will begin with.
For practitioners, the headline is that a single social-media publication can carry the serious harm element where the evidence of impact supports it — the medium’s informality does not immunise the publisher, and the assessment remains anchored in the actual and likely consequences for the plaintiff’s reputation.
The Coming High Court Fight
Mr Latham has signalled he will seek special leave to appeal, contending that the Full Court erred in its construction of the serious harm threshold and pointing to what he describes as open conflict in the authorities. If the High Court takes the case, it would be its first consideration of s 10A — a decision that would bind every Australian court and settle the questions that Latham, MacInnes v Wilson (itself now before the Full Court) and Singh v Singh have been working through case by case.
The appellate landscape, in other words, is suddenly crowded: two Full Court proceedings and a prospective High Court special leave application, all turning on the same statutory element. As we set out in our five-year retrospective, s 10A has become the first and often final battlefield of Australian defamation litigation — and the battlefield is now appellate.
What It Means in Practice
For plaintiffs: the decision confirms that a properly evidenced claim over even a single post can succeed — but the emphasis is squarely on properly evidenced. The material that carries s 10A — reach, grapevine spread, identifiable reputational consequences — must be assembled from the outset, beginning with a concerns notice that puts the harm on the record.
For defendants and publishers: appellate confirmation of a $140,000 award over one post is a caution against treating social media as a low-stakes arena. Early, reasonable resolution offers remain the most effective way to limit exposure.
For everyone: until the High Court speaks, Latham v Greenwich is the authority trial courts will apply. Any serious harm strategy — prosecuting or defending — should now be built on its framework.
If you have been defamed — or accused of defamation — Matrix Legal acts exclusively in defamation matters, Australia-wide. Call 1800 950 627 for a free case assessment.
Frequently Asked Questions
What did the Full Court decide?
It dismissed both the appeal and cross-appeal, leaving the defamation finding over a single X post and the $140,000 award (including aggravated damages) intact.
Why does it matter beyond the parties?
It is the most comprehensive appellate treatment of s 10A to date — binding guidance on how serious harm is proved, which every trial court will now apply.
Is the High Court involved?
Not yet. Mr Latham has indicated he will seek special leave, arguing the Full Court erred on the serious harm threshold. If leave is granted, it would be the High Court’s first s 10A case.
Mark Stanarevic is the principal of Matrix Legal, Australia’s specialist defamation law firm. This article is general information, not legal advice.