Tensions - and voices - rose on Thursday as Donald Trump's lawyer hit back against prosecutors, accusing their star witness repeatedly of lying.

On the most tense day yet of cross-examination, Michael Cohen, Mr Trump's former fixer, described talking to the former president directly about a hush-money payment to an adult film star.

But attorney Todd Blanche all but shouted Cohen's testimony was "a lie."

Records, he said, show Cohen called Mr Trump's bodyguard about a prank caller.

Mr Blanche's theory of the phone call was designed to sow doubt on Cohen's third day on the stand, as the jury watched the furious exchange with intense focus.

Following the heated moment, Mr Blanche stormed back to the defence table and sat down next to his client. When the judge announced an afternoon recess, there was a collective exhale in the room.

Mr Trump is charged with 34 felony counts of falsifying business records, for allegedly disguising payments to Cohen as legal expenses when they were in fact reimbursements for paying off film star Stormy Daniels, who claims she had sex with him.

Prosecutors allege Mr Trump sought to keep damaging information from the public to protect his 2016 presidential campaign. Mr Trump has pleaded not guilty to all counts and denied having sex with Ms Daniels.

On the stand Thursday under pressure, Cohen maintained that his previous testimony was true, and that he spoke to Mr Trump about the payout to Ms. Daniels on a call on 24 October 2016.

Earlier this week, prosecutors asked Cohen about the call to help establish Mr Trump's alleged direct knowledge of the payoff scheme. Cohen testified that he kept his boss aware during every step of the process of paying Ms Daniels.

As the man at the centre of the payout, Cohen's testimony is crucial for prosecutors to prove whether or not Mr Trump had knowledge of the allegedly fraudulent reimbursement plan.

But Cohen's criminal record, history of lying to Congress, and profane public criticism of Mr Trump makes him a flawed witness. In 2018, he pleaded guilty to federal campaign finance crimes over the hush-money payment but maintains that he sent the money at Mr Trump's direction.

The defence seized on Cohen's credibility issues for nearly two days and sought to paint him as a liar with a vendetta against Mr Trump.

On Thursday morning, Mr Blanche played recordings from Mr Cohen's podcast, Mea Culpa, where the witness expressed a desire to see the former president go through the booking process and said of Mr Trump, "I want this man to go down.''

Mr Blanche also confronted Cohen with an X post where he called the former president "Dumbass Donald."

"Does the outcome of this trial affect you personally?" Mr Blanche asked him.

"Yes," Cohen replied.

The president's attorney pressed Cohen repeatedly about his guilty plea for lying to Congress, and aggressively questioned Cohen about previous statements that he did not believe prior tax evasion charges he pleaded guilty to were fair.

Several hours of similar questioning all led to the dramatic showdown over the 24 October 2016 phone call.

Mr Blanche first asked Cohen if he recalled receiving harassing calls in late October 2016. Cohen confirmed he had.

Mr Blanche then displayed communications between Cohen and Mr Trump's bodyguard, Keith Schiller, on 24 October discussing how to deal with the prank calls.

Amid their discussions about the prank caller, is a call between Cohen and Mr Schiller, that Cohen previously testified he made to discuss the payout to Ms Daniels with Mr Trump. That call lasted a minute and 36 seconds.

Mr Blanche expressed scepticism that Cohen could have discussed both the prank caller and the six-figure payout in such a brief period.

But Cohen countered that part of that call was about "the 14-year-old" who was behind the calls. He knew that Mr Schiller was with their boss at the time, and the call was about more than just the harassment, he said.

Cohen insisted he always ran "everything by the boss" immediately, and that he did so on that call.

The response drew a dramatic reaction from Mr Blanche: "That. Was. A. Lie," he declared loudly.

Numerous Republican members of Congress filled the benches behind Mr Trump on Tuesday in a show of partisan support.

A Trump campaign spokeswoman attended, as did his son, Eric Trump.

Reps. Matt Gaetz of Florida, Lauren Boebert of Colorado, and Andy Biggs were among the entourage, which was so large that some lawmakers had to sit in the back of the courtroom.

Cohen's testimony has piqued public interest. The line to get into court stretched down the block Thursday morning, and journalists and members of the public had hired line sitters to save them a spot overnight.

One line sitter, whose employer did not show, offered others in line $400 for her spot.

Despite the immense public interest, however, the defendant did not express much enthusiasm in the courtroom: Mr Trump sat back silently in his seat for most of the morning session. At a few points, he focused intently on the cross-examination.

Though one of his biggest public nemeses sat just a few feet to his right, most of the time, Mr Trump just stared straight ahead.

"I think it was a very interesting day," Mr Trump told the waiting cameras as he left the courtroom. "A fascinating day."