Former lawyer’s testimony viewed as key in former president’s criminal prosecution six months ahead of election.

The star prosecution witness in Donald Trump’s hush money trial, Michael Cohen, is set to take the stand to testify against the former president.

Trump’s former lawyer and personal fixer, is due in court on Monday. The Manhattan district attorney hopes that the testimony of the key witness would help influence the verdict in the first-ever criminal case against a US president, sitting or former.

Cohen’s expected appearance in the New York courtroom signals that the closely-watched trial is entering its final stretch. Prosecutors say they may wrap up their presentation of evidence by the end of the week.

Cohen is set to testify about his role in arranging hush money payments on Trump’s behalf, including to adult film actress Stormy Daniels.

Daniels told jurors last week that a payment of $130,000 that she received in 2016 was meant to prevent her from going public about a sexual encounter she says she had with Trump at a celebrity golf tournament a decade earlier.

Trump is accused of falsifying business records to reimburse Cohen for the payment on the eve of the 2016 presidential election when the story could have proved politically fatal. Prosecutors say the reimbursements were logged as legal expenses to conceal their true purpose.

The Republican presidential candidate has denied the allegations.

Defence lawyers are expected to try to paint Cohen, who once said he would “take a bullet” for Trump, as untrustworthy. They are also expected to cast him as vindictive and agenda-driven.

Since their fallout, the fixer-turned-foe has emerged as a relentless and sometimes crude critic of Trump. Last week he appeared in a live TikTok stream wearing a shirt featuring a figure resembling Trump behind bars and wearing handcuffs.

Five years ago, Cohen pleaded guilty to federal charges related to the payments and to lying to Congress. Trump’s defence will highlight the prosecution’s reliance on a witness with such a record.

Other witnesses, including former National Enquirer publisher David Pecker and former Trump adviser Hope Hicks, have testified at length about the role Cohen played in arranging to stifle stories that were feared to be harmful to Trump’s 2016 candidacy.

Jurors also heard an audio recording of Trump and Cohen discussing a plan to buy the rights to a story of a Playboy model, Karen McDougal, who has said she had an affair with Trump.

The trial is taking place six months before the November election, when the presidential hopeful will try to defeat Democratic President Joe Biden.