'A real headache': How Cohen makes or breaks Trump trial

The prosecution's star witness in Donald Trump's Manhattan criminal trial could also be its biggest liability.

Michael Cohen, Mr Trump's former personal attorney, is expected to take the stand to testify against the man he once reverently referred to as "The Boss."

Cohen made the hush money payment at the centre of the case, a sum which the prosecution alleges was fraudulently reimbursed by Mr Trump. He could provide essential testimony for prosecutors.

But outside the courtroom, on podcasts, television and social media, Cohen has not exactly helped their case.

He has mocked Mr Trump on X, calling him "sleepy Donald" and has used a profane nickname referring to the former president. Cohen also has posted memes that appear to show Mr Trump in prison-uniform orange, and joked on TikTok about Mr Trump being incarcerated.

"Trump 2024?" he said during one TikTok stream, reported by ABC News. "More like Trump 20-24 years."

Cohen's rogue behaviour, coupled with his very real criminal record, has opened the door for Mr Trump's defence to cast doubt on this crucial player.

"He's a real headache," said Lance Fletcher, a former Manhattan prosecutor who now practises criminal defence. "He's doing everything as a prosecutor you don't want your witness to do. He's got all sorts of credibility problems."

An attorney representing Cohen declined to comment for this story.

In 2018, Cohen pleaded guilty to eight felony counts including tax offences, fraud and campaign finance violations. The latter charge stemmed from the very same hush money payment at the heart of Mr Trump's case.

He also pleaded guilty to lying to Congress - a fact Mr Trump's attorneys have brought up in this trial and during a separate civil case.

Mr Trump is charged with 34 counts of falsifying business records for allegedly reimbursing Cohen for making a $130,000 hush money payment to adult film star Stormy Daniels, then trying to disguise records of the payment as legal expenses.

He has pleaded not guilty and denied having an affair.

Todd Blanche, Mr Trump's lead attorney, tried to undercut Cohen as a witness in his opening statement. He said Cohen remained "obsessed" with Trump "to this day," and that he "rants and raves" about the former president.

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"I submit to you that he cannot be trusted," Mr Blanche said.

Mr Fletcher agrees with the defence's strategy. "You almost want to make the case about him," he said.

Mr Blanche and his colleagues could bring up Cohen's previous comments while he's on the stand, and call into question his motivation for providing damaging testimony against Mr Trump. His attorneys already have alleged Cohen is profiting off Mr Trump's legal problems through his podcast, TikTok streams, and books.

If Cohen testifies, "maybe you can get him upset, maybe he starts yelling and screaming and coming apart at you," Mr Fletcher said.

During her time as a prosecutor, former New York State Acting Supreme Court Justice Diane Kiesel used to have a saying: "I don't go to central casting for my witnesses."

In other words, prosecutors do not always get the perfect witness to prove their case - some, while providing essential testimony, are flawed. Manhattan District Attorney Alvin Bragg is in a similar position with Cohen, she said.

"Who do you think is going to be making hush money payments to a porn star?" Judge Kiesel said. "Some upstanding member of the bar... who everyone looks up to as a paragon of legal ethics?"

She said Mr Bragg's team must "go through every single thing that Michael Cohen has to say" and offer corroborating evidence to convince the jury.

Prosecutors already have acknowledged Cohen's flaws to jurors.

During opening statements, assistant district attorney Michael Colangelo told the jury: "You will need to keep an open mind" about Cohen, and "keep in mind all the evidence that corroborates Michael Cohen's testimony".

Prosecutors have introduced a paper trail of texts, emails, phone calls, bank records and legal contacts Cohen left as he brokered payouts to Ms Daniels and another woman, Playboy model Karen McDougal, in exchange for their silence.

They have called on multiple corroborating witnesses, like former tabloid publisher David Pecker and Ms Daniel's former attorney Keith Davidson, who could shed light on events involving Cohen.

But prosecutors cannot make Cohen stop talking.

"When I was a prosecutor, I [occasionally] wished I could give witnesses a gag order, but you can't," Mr Fletcher said. "They have the same rights and powers as regular citizens."

The district attorney's office did not return a request for comment.

On 24 April, Cohen announced - likely to the relief of prosecutors - that he would impose a gag order on himself.

"Despite not being the gagged defendant, out of respect for Judge Merchan and the prosecutors, I will cease posting anything about Donald on my X (formerly Twitter) account or on the Mea Culpa Podcast until after my trial testimony," Mr Cohen posted. "See you all in a month (or more).

Whether or not he keeps his word remains to be seen.

"The district attorney can read him the riot act all they want," said former Judge Kiesel. "But if he's not gonna listen, he's not gonna listen."