Former US President Donald Trump is at his civil fraud trial in New York as his ex-lawyer gives evidence against the man for whom he once vowed he would “take a bullet”.
Cohen spent a decade as Mr Trump’s “fixer” before turning on him in a 2018 federal case.
It’s the first time in five years the arch-foes have been in the same room.
A judge in the case has already ruled Mr Trump inflated the value of his properties to secure favourable loans.
In addition to this civil trial, Mr Trump is battling four criminal cases while he campaigns for the White House.
On the witness stand, Cohen recalled how his relationship with Mr Trump began in 2007, after he was introduced to him through Mr Trump’s son, Don Jr.
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It was then that Mr Trump asked Cohen to leave his “sleepy old [law] firm,” as the former president called it, to work for the Trump Organization, Cohen testified.
While working for the Trump Organization, Cohen said his responsibility was to “reverse engineer” different assets to increase their value based on a number that Mr Trump “arbitrarily elected”.
Mr Trump sat with a stony face and folded arms as Cohen entered the Manhattan courtroom.He appeared to look in his former employee’s direction as he took the stand, but said nothing.
As he entered court on Tuesday morning, Mr Trump called Cohen “a proven liar”.
The Republican front-runner for the 2024 presidential election added: “We did nothing wrong and that’s the truth.”
Mr Trump has been occasionally attending the trial on a voluntary basis and is expected to testify himself at some point.
Cohen was handed a three-year jail sentence in 2018 for lying to Congress and over hush payments he made on Mr Trump’s behalf.
He was released from prison in 2020 to serve most of his remaining sentence in home confinement.
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Outside court, Cohen told reporters: “This is about accountability, plain and simple.”
Earlier, he said of coming face-to-face with his former boss: “I look forward to the reunion. I hope Donald does as well.”
Cohen is a key witness in the civil fraud trial. During congressional testimony in 2019, he said Mr Trump had inflated his property values.
His evidence to lawmakers sparked an investigation led by New York Attorney General Letitia James.
Ms James, a Democrat and the state’s top prosecutor, is seeking a fine of $250m (£205m) and a ban on Mr Trump doing business in his home state.
In late September, the judge, Arthur Engoron, ruled Mr Trump had committed fraud through repeatedly misrepresenting his wealth by hundreds of millions of dollars.
Judge Engoron ordered that a court-appointed receiver take over companies that run Trump Tower and other crown jewels of the ex-US president’s real estate portfolio. An appeals court has blocked that move for now.
The judge also fined the former president $5,000 on Friday for failing to remove an online post mocking a court clerk – in contravention of a gag order.
He has repeatedly denied any wrongdoing, arguing that his assets were actually undervalued.
Mr Trump has also previously sued Cohen, accusing him of “spreading falsehoods” and breaking a confidentiality agreement.
That lawsuit was halted earlier this month, but a Trump spokesperson said it will be refiled at a later date.
Additional reporting by Nadine Yousif