Michael Cohen, the prosecution's star witness in Donald Trump's hush money trial, is expected to take the stand Monday, according to multiple sources familiar with the case.

Trump's former attorney and "fixer," Cohen made the $130,000 payment to Stormy Daniels that sits at the center of the case, in order to buy her silence and help Trump's electoral prospects in the 2016 presidential election.

Prosecutors accuse of Trump falsifying business records when he repaid Cohen the $130,000.

Former Trump White House aide Madeleine Westerhout is set to resume her testimony this morning in former President Donald Trump's New York criminal trial.

For prosecutors, Westerhout's testimony yesterday offered a detailed picture of how Trump approached his personal finances while serving as president -- including how he signed personal checks for his then-attorney Michael Cohen and others.

Defense attorneys, meanwhile, appeared to use Westerhout to highlight Trump's character following hours of abrasive testimony from Stormy Daniels.

"He never once made me feel like I didn't deserve that job and I didn't belong there, especially in an office filled with older men," Westerhout told jurors about working by Trump's side for over two years. "He was a really good boss. I hope he respected me in my job, and I just found him very enjoyable to work for."

Westerhout at one point broke down in tears on the witness stand while recounting to the jury how she lost her job after she shared private details of Trump's family with reporters at an off-the-record dinner.

"That mistake, eventually -- ultimately, cost me my job, and I am very regretful of my youthful indiscretion," Westerhout said while crying.

Judge Juan Merchan dismissed court for the day following the late hearing.

Trump, speaking to reporters on his way out of the courtroom, railed against the judge.

"Everybody saw what happened today -- I don't think we have to do any expert explaining," Trump said. "I'm not allowed to anyway because this judge is corrupt," he said, criticizing Merchan -- who is not protected by the limited gag order in the case.

"I got to get back on the campaign trail. I'm not supposed to be here. We are so innocent," Trump said.

-ABC News' Kelsey Walsh and Mike Pappano

Merchan took defense attorney Susan Necheles to task for her failure to object to a line of inquiry about whether or not Donald Trump used a condom during his alleged encounter with Stormy Daniels.

"For the life of me, I don't know why Ms. Necheles didn't object," the judge said.

Merchan emphasized that Daniels testimony was necessary because Trump's lawyers continue to deny the encounter occurred.

"That pits your client's words against Ms. Daniels' word," the judge said.

"These details add a sense of credibility if the jury chooses to believe them," Merchan said. "Your motion for a mistrial is denied."