THE COURT OF Appeal has dismissed an appeal by Gemma O’Doherty to a defamation case taken by the brother of the late journalist Veronica Guerin, and criticised O’Doherty’s use of artificial intelligence in her legal submissions.

In a judgment delivered yesterday, Judge Caroline Costello upheld an earlier High Court decision refusing to strike out the case, meaning it will now proceed towards a full retrial before a judge and jury.

The case centres on social media posts and a video published by O’Doherty in 2019, which Jimmy Guerin, a Fingal County councillor, says defamed him by claiming that he was a convicted paedophile.

He sued O’Doherty, a former journalist with the Irish Independent, over the postings on Twitter (X), Facebook and her own internet video broadcast portal.

The broadcast includes a statement of “how the brother of Veronica Guerin” was found with large quantities of child sexual abuse images.

O’Doherty maintains she was referring instead to his brother, Martin Guerin, who was convicted that year of child pornography offences and received a two-and-a-half year suspended prison sentence.

A previous trial over the alleged defamation collapsed in 2023 after the jury failed to reach a verdict, and a retrial was later ordered.

O’Doherty had asked the courts to throw out the case, arguing it was abusive, bound to fail, and an attack on press freedom. However, the Court of Appeal rejected those arguments.

The court found there were valid grounds for the defamation case and no basis to throw it out before a full hearing.

Judges also dismissed O’Doherty’s claims that the proceedings were an attempt to silence her as a journalist, or that she could not receive a fair trial, describing some of her arguments as unsupported.

Separately, the judgment highlighted problems with O’Doherty’s use of AI to prepare her written submissions.

O’Doherty’s use of AI for her submitted files seemingly churned out false legal backing, which the court called “hallucinations”.

“The submissions included references to authorities which simply did not exist,” Judge Costello said.

“This is an inherent and well-known risk of using AI to write legal submissions. The defendant did not apparently verify the existence of the authorities she cited, or that the cases relied upon actually supported the propositions advanced.

“Neither did she notify the solicitors for the plaintiff that she had prepared her submissions with the assistance of AI.”

The judgment noted that the false citations caused unnecessary work and expense for the other side, who had been required “fruitlessly to attempt to locate the hallucinated authorities and thereby needlessly added to the costs of the plaintiff in the appeal”.

Judge Costello said people are allowed to use AI tools to help with legal research, but must do so carefully.

The court also set out guidance for future cases, saying that anyone using AI in legal submissions should make that clear and must independently verify the accuracy of what they rely on.

“For the avoidance of doubt, I wish to make it clear that I do not believe that the defendant intended to mislead the court or that she was actually aware of the fact that some of the cases cited in her written submissions were hallucinations,” Judge Costello said.

The appeal was dismissed in full, with the court indicating that Jimmy Guerin, who was successful, should be entitled to his legal costs.