Michael Cohen is prepared to share who signed the $35,000 monthly checks he received in reimbursement for his hush-money payments to Stormy Daniels, according to a person with knowledge of his upcoming congressional testimony. Cohen is expected to bring documentation revealing who signed the checks, according to that source.

The checks are important because Cohen pleaded guilty to violating campaign-finance laws by facilitating those payments, which went to porn star Stormy Daniels to buy her silence about an alleged sexual encounter with Donald Trump. The efforts to repay him for that disbursement could spell legal trouble for the person who signed the checks.

Cohen is also prepared to testify that he has evidence President Donald Trump committed crimes during his time in office, according to that person.

Trump signed some of the checks, the Wall Street Journal reported Tuesday night, citing a source familiar with his planned testimony. Cohen began receiving the checks after Trump took office, the Journal said.

Rudy Giuliani, Trump’s personal lawyer, has claimed publicly that Cohen was paid a $35,000 monthly retainer for legal services in reimbursement. On Sean Hannity’s Fox News show last May, Giuliani said Trump did not know “the specifics” of the scheme to reimburse Cohen. Cohen is prepared to say Giuliani’s claim of the existence of a retainer agreement is false, according to the person, who said the monthly payments appear to be part of a “cover-up.”

Cohen will testify on Capitol Hill for three consecutive days this week: today behind closed doors to the Senate intelligence committee, tomorrow in public before the House Committee on Oversight and Reform, and Thursday behind closed doors to the House intelligence committee.

For years, Cohen was Trump’s most loyal fixer. He once infamously claimed to a Daily Beast reporter that there was no such thing as spousal rape (a claim he later recanted), and threatened to sue the publication for reporting on claims one of Trump’s ex-wives made about him.

“I will make sure that you and I meet one day while we’re in the courthouse,” Cohen said in 2015, when Trump’s campaign was taking off. “And I will take you for every penny you still don’t have. And I will come after your Daily Beast and everybody else that you possibly know. So I’m warning you, tread very fucking lightly, because what I’m going to do to you is going to be fucking disgusting. You understand me?”

Cohen did not come after The Daily Beast. But he worked with Trump throughout his presidential campaign, frequently appearing as a media surrogate. After Trump’s inauguration, Cohen failed to land a coveted administration job. So he tried to cash in on his perceived influence in Trumpworld, signing a deal with AT&T and allying himself with lobbying mega-firm Squire Patton Boggs.

But his Trump-adjacent glory didn’t last. In January 2018, The Wall Street Journal broke the news that he arranged a six-figure hush-money payment to Daniels. A federal investigation into the payments ensnared Cohen, and in the months after, he insisted he would never turn on Trump. But eventually, amid a dispute about who would pay Cohen’s swollen legal bills, he flipped—retaining new counsel, bringing on Clinton fixer Lanny Davis as his media representative, and proclaiming that his loyalty to his family and country superseded his loyalty to Trump.

Trump, in typical fashion, fired back.

Months later, Cohen folded. He pleaded guilty to a host of crimes including a campaign-finance violation. He later cooperated with Special Counsel Robert Mueller’s investigation into Russian efforts to interfere in the 2016. In December, he was sentenced to three years in prison. He is set to begin serving the sentence in May.