WASHINGTON — The dramatic public testimony to Congress on Wednesday morning by President Trump’s former lawyer, Michael D. Cohen, could intensify the legal issues facing the president in the criminal and civil investigations that are swirling around him, legal experts said.
Mr. Cohen’s testimony before the House Oversight and Reform Committee was a remarkable personal and political rebuke to the president from a lawyer who served Mr. Trump with fierce loyalty for more than a decade.
In his prepared testimony and about five hours of grilling by lawmakers, Mr. Cohen — who has pleaded guilty to lying to Congress and will go to prison for his crimes — blasted the president as a “racist,” a “con man” and a “cheat.”
But legal experts said several of the specific allegations by Mr. Cohen in his opening statement could be relevant to questions about whether Mr. Trump participated in a conspiracy to affect the 2016 election, violated campaign finance laws and obstructed justice in an effort to deflect investigations.
The experts cautioned that nothing Mr. Cohen said drastically altered what was known about any legal case against the president. The relevant laws are complex, and the president’s lawyers have repeatedly argued that he did not violate them. And perhaps most important, they note, there is a Justice Department policy that asserts that a president may not be indicted while in office.
Still, Mr. Cohen’s testimony surfaced some new information that could be relevant to Robert S. Mueller III, the special counsel, or other prosecutors investigating cases touching on the president. Here are some examples:
Hush Money for Porn Star
In his prepared remarks, Mr. Cohen described in detail how Mr. Trump personally reimbursed Mr. Cohen for the $130,000 hush money payment to Stormy Daniels, the pornographic film actress whose legal name is Stephanie Clifford, to ensure her silence about an affair with Mr. Trump.
“In February 2017, one month into his presidency, I’m visiting President Trump in the Oval Office for the first time,” Mr. Cohen said. “It’s truly awe-inspiring, he’s showing me around and pointing to different paintings, and he says to me something to the effect of ‘Don’t worry, Michael, your January and February reimbursement checks are coming. They were FedExed from New York and it takes a while for that to get through the White House system.’”
Richard L. Hasen, an election law professor at the University of California, Irvine School of Law, said prosecutors could use Mr. Cohen’s description of the payments from Mr. Trump to bolster a charge of campaign finance violations.
“To the extent that these were illegal campaign finance contributions, which were reimbursed and not reported, here is more evidence that Trump was conspiring to violate campaign finance laws as president,” Mr. Hasen said.
He noted, however, that campaign finance laws — which are complex — require proof that a person was willfully violating them. Mr. Cohen’s testimony does not prove that Mr. Trump knew that the payments he was making were illegal — something that prosecutors would have to prove if they wanted to charge the president.
WikiLeaks and Emails
In his testimony, Mr. Cohen described a moment when he said Roger J. Stone Jr., one of Mr. Trump’s top political operatives, called the president to tell him about a conversation with Julian Assange, the WikiLeaks founder.
“I was in Mr. Trump’s office when his secretary announced that Roger Stone was on the phone. Mr. Trump put Mr. Stone on the speakerphone,” Mr. Cohen said. “Mr. Stone told Mr. Trump that he had just gotten off the phone with Julian Assange and that Mr. Assange told Mr. Stone that, within a couple of days, there would be a massive dump of emails that would damage Hillary Clinton’s campaign.”
Mr. Cohen added: “Mr. Trump responded by stating to the effect of ‘wouldn’t that be great.’”
Legal experts cautioned that just proving that Mr. Trump knew about the WikiLeaks plans to leak damaging documents ahead of time would not necessarily prove that the president or his campaign were guilty of conspiracy. Prosecutors would have to prove that Mr. Trump and the campaign actively engaged in coordinating with Russians to distribute the documents or took other actions to affect the outcome of the election.
The question of contacts between WikiLeaks and the Trump campaign is central to the issue of whether there was any conspiracy between the campaign and Russia. It is not known what Mr. Trump might have told Mr. Mueller’s team about what, if anything, he knew about WikiLeaks’ plans or about contacts between Mr. Stone and Mr. Assange.
Peter Zeidenberg, a former federal prosecutor, said that if Mr. Cohen is telling the truth, and if Mr. Trump claimed to Mr. Mueller in his sworn, written testimony that he was not aware of any contacts between Mr. Stone and Mr. Assange, that could be a crime.
“When you lie in that context, it’s not only perjury but it’s obstruction of justice, too,” Mr. Zeidenberg said.
Campaign Finance Violations
Mr. Cohen’s testimony about Mr. Stone’s conversation with Mr. Trump could also open the president up to further campaign finance violations, Mr. Hasen said.
Federal law bars campaigns from taking anything of value from foreign entities. The conversation with Mr. Stone could be used to help prove that Mr. Trump and his campaign knowingly accepted valuable help from WikiLeaks in his efforts to defeat Hillary Clinton during the 2016 presidential campaign.
“If it’s true that Stone was directly in communication with Assange while also communicating with Trump and the Trump campaign, there’s the potential for a violation of the campaign finance laws involving foreign contributions,” Mr. Hasen said.
He was quick to point out that prosecutors would need to have more evidence than just the conversation between Mr. Stone and Mr. Trump. “There are a lot more steps that we would need to conclude that Trump or the Trump campaign acted illegally with regard to WikiLeaks,” he said.
Trump Tower Moscow
In his prepared remarks, Mr. Cohen disputed a report this year from BuzzFeed News that Mr. Trump “personally instructed him to lie” to Congress about negotiations to build a Trump Tower in Moscow — an allegation that could lead to criminal charges if true.
“Mr. Trump did not directly tell me to lie to Congress,” Mr. Cohen said. “That’s not how he operates.”
But Mr. Cohen added that the president implicitly instructed him to lie about the Moscow deal by repeatedly lying about it himself.
“In conversations we had during the campaign, at the same time I was actively negotiating in Russia for him, he would look me in the eye and tell me there’s no business in Russia and then go out and lie to the American people by saying the same thing,” Mr. Cohen said. “In his way, he was telling me to lie.”
Mr. Cohen also said later during the hearing that Jay Sekulow, one of Mr. Trump’s lawyers, reviewed the false testimony that Mr. Cohen had prepared to give to Congress in May 2017 related to the Trump Tower Moscow project. Mr. Cohen suggested that Mr. Sekulow made changes that related to the timing of the project.
“There were several changes made, including how we were going to handle that message which was — the message, of course, being the length of time that the Trump Tower Moscow project stayed and remained alive,” Mr. Cohen said Wednesday.
Legal experts said the law did not require prosecutors to prove that Mr. Trump explicitly told Mr. Cohen to lie to Congress. But they also said that any effort to obscure the timing of the negotiations over the construction project could be used as evidence of motive in efforts to build a conspiracy case against the president.
“If you’re going to make a case of conspiracy with the Russians, that’s going to be front and center,” Mr. Zeidenberg said.
Trump Tower Meeting
Mr. Cohen testified that he overheard a conversation that he believed proved that Mr. Trump knew about a campaign meeting between his top campaign aides and people connected with Russians.
“I recalled Don Jr. leaning over to his father and speaking in a low voice, which I could clearly hear, and saying: ‘The meeting is all set.’ And I remember Mr. Trump saying: ‘O.K. good. Let me know,’” Mr. Cohen said.
The president’s knowledge of the Trump Tower meeting has been at the center of questions about whether his campaign conspired with Russians to affect the outcome of the presidential election. Legal experts said Mr. Cohen’s testimony could be relevant to any case that might be built against the president by Mr. Mueller.
Violations by Trump Charity
In his remarks, Mr. Cohen said Mr. Trump directed him to use Trump Foundation funds to acquire a portrait of Mr. Trump.
“The portrait was purchased by the fake bidder for $60,000,” Mr. Cohen said. “Mr. Trump directed the Trump Foundation, which is supposed to be a charitable organization, to repay the fake bidder, despite keeping the art for himself.”
Legal experts said that could be a civil violation of state laws governing charitable foundations. Mr. Trump’s foundation has been under investigation for its operations, including similar purchases of another portrait.
In December, the foundation announced it would shut down after the New York attorney general accused it of “functioning as little more than a checkbook to serve Mr. Trump’s business and political interests.”
Inflating Net Worth
Among the allegations Mr. Cohen made during his testimony was that Mr. Trump had tried to inflate his own net worth to Deutsche Bank when he approached the bank about lending him money to buy the Buffalo Bills.
To back up his claim, Mr. Cohen provided the committee financial documents that listed Mr. Trump’s personal assets and liabilities in 2011, 2012 and 2013.
Providing false information to a bank to get a loan can lead to charges of bank fraud or conspiracy, according to legal experts. But the process of determining the value of property is also highly subjective, which could limit the president’s legal exposure.
Other Legal Unknowns
In hours of testimony, Mr. Cohen mostly touched on legal questions that have already been in public view. But legal experts said it was important to remember how much legal work had been kept secret by the prosecutors running the various investigations.
That reality was underscored when Representative Raja Krishnamoorthi, Democrat of Illinois, asked Mr. Cohen whether there was “any other wrongdoing or illegal act that you are aware of regarding Donald Trump that we haven’t yet discussed today.”
Mr. Cohen’s answer was tantalizing: “Yes, and again those are part of the investigation that’s currently being looked at by the Southern District of New York.”
He did not elaborate.