Michael Cohen, the prosecution's star witness in Donald Trump's criminal trial, is on the stand on Monday.

Trump's former personal lawyer and so-called fixer, is considered the most important witness for the Manhattan district attorney's criminal case against the former president.

Cohen is expected to testify about his role in arranging hush money payments during Trump's first presidential campaign.

One of those payments allegedly went to porn actor Stormy Daniels, who testified in detail last week about an alleged sexual encounter with Trump that he denies took place.

Daniels was paid $130,000 to keep quiet about her story, according to previous testimony. The accounting of that payment is the heart of the prosecution case.

Trump faces 34 felony counts of falsifying business records in an alleged effort to hide the payment as legal expenses.

The defense team is expected to try to paint Cohen as an "admitted liar" who is simply out to get revenge on his former boss. Cohen pleaded guilty to federal charges after lying to Congress.

Other witnesses, including former National Enquirer publisher David Pecker have testified about Cohen's role working to kill stories that were thought to be potentially harmful to Trump during the 2016 presidential campaign.

Prosecutors say they may wrap up their presentation of evidence by the end of the week.

During a rally on Saturday in Wildwood, New Jersey, Trump railed against the case, trying to claim President Joe Biden for his legal woes, calling the case a "Biden show trial."