Michael Cohen, Donald Trump’s one-time personal lawyer and fixer, says he unwittingly passed on to his lawyer bogus artificial intelligence-generated legal case citations he got online before they were submitted to a judge.

Cohen made the admission in a court filing unsealed on Friday in Manhattan federal court after a judge earlier this month asked a lawyer to explain how court rulings that do not exist were cited in a motion submitted on Cohen’s behalf.

Judge Jesse Furman had also asked what role, if any, Cohen played in drafting the motion.

The AI-generated cases were cited as part of written arguments a lawyer made to try to bring an early end to Cohen’s court supervision after he served more than a year behind bars.

Cohen had pleaded guilty in 2018 to tax evasion, campaign finance charges and lying to Congress, saying Mr Trump directed him to arrange the payment of hush money to a porn actor and to a former Playboy model to fend off damage to his 2016 presidential bid.

Cohen, who was disbarred five years ago, said in a declaration submitted to the judge on Thursday that he found the citations by doing research through Google Bard and was unaware that the service could generate nonexistent cases.

He said he uses the internet for research because he no longer has access to formal legal research sources.

“As a non-lawyer, I have not kept up with emerging trends (and related risks) in legal technology and did not realise that Google Bard was a generative text service that, like Chat-GPT, could show citations and descriptions that looked real but actually were not,” Cohen said.

“Instead, I understood it to be a super-charged search engine and had repeatedly used it in other contexts to (successfully) find accurate information online.”

He blamed his lawyer and longtime friend David Schwartz for failing to check the validity of his citations before submitting them to the judge, though he asked that the judge dispense mercy toward Mr Schwartz, calling his failure to check the citations an “honest mistake” and “a product of inadvertence, not any intent to deceive”.

Mr Schwartz did not immediately respond to a request for comment.

In a declaration filed with the court, Mr Schwartz said he thought drafts of the papers to be submitted to the judge to dissolve Cohen’s probation early were reviewed by E Danya Perry, a former federal prosecutor now in private practice who also represents Cohen. He said he never reviewed what he thought was another lawyer’s research.

Ms Perry, who discovered that the cited cases were bogus after seeing the court filing, said Mr Schwartz’s claim that he came to “believe” that the citations came from her were “incorrect and I believe, far-fetched, as I had no involvement in any back-and-forth — not directly with Mr Schwartz or his paralegal and not even indirectly through Mr Cohen.”

When she learned of them, Ms Perry reported the false case citations to the judge and federal prosecutors.

“Mr Cohen engaged in no misconduct and should not suffer any collateral damage from Mr Schwartz’s misstep,” Ms Perry wrote in her submission to the judge.

In discussing possible sanctions earlier this month, the judge noted that it was the second time this year that a judge in Manhattan federal court has confronted lawyers over fake citations generated by artificial intelligence.

Two lawyers in an unrelated case were fined 5,000 dollars (£3,921) for citing bogus cases that were invented by ChatGPT, the AI-powered chatbot.

In entering the 2018 guilty plea, Cohen did not name the two women who received hush money or even Mr Trump, recounting instead that he worked with an “unnamed candidate” to influence the 2016 election.

But the amounts and the dates lined up with 130,000 dollars (102,000) paid to adult film actress Stormy Daniels and 150,000 dollars (£117,600) that went to Playboy Playmate Karen McDougal to buy their silence in the weeks and months leading up to the presidential election, which Mr Trump, a Republican, won over Democrat Hillary Clinton. Ms Daniels and Ms McDougal claimed to have had affairs with Mr Trump, which he denied.

Mr Trump’s personal lawyer at the time of Cohen’s 2018 guilty plea, former New York mayor Rudy Giuliani, noted in a statement that there was “no allegation of any wrongdoing against the president in the government’s charges against Mr Cohen”.