In their effort to discredit President Donald Trump’s perceived enemies, close allies of the President have received key documents and information from a Ukrainian oligarch wanted in the U.S. on corruption charges, according to five people directly involved in this effort and two other people familiar with it.

The information came from the legal team of Dmitry Firtash, a wealthy industrialist with assets across Europe, who has spent the last five years in Vienna fighting extradition to the U.S. on bribery and racketeering charges. The U.S. Department of Justice said in 2017 he was among the “upper echelon associates of Russian organized crime”—something Firtash vigorously denies, along with all charges against him.

As part of his legal defense, Firtash’s lawyers have gathered documents that make controversial allegations against former special counsel Robert Mueller and former Vice President Joe Biden. Firtash’s lawyers have passed these documents and other information to associates of Trump’s personal lawyer Rudy Giuliani.

In his frequent appearances on cable news, Giuliani has presented some of these documents to the American public as evidence for his claims of wrongdoing by Mueller and Biden. The key document is an affidavit from a former Ukrainian prosecutor who accuses Biden of corruption. “The witness I’m relying on,” Giuliani told Fox News on Oct. 6, was the prosecutor Viktor Shokin. “That’s the affidavit I put out,” Giuliani added. He did not mention that the affidavit was obtained by the Firtash legal team. At the beginning of the document, Shokin writes that he is making the statement “at the request of lawyers acting for Dmitry Firtash.”

Asked about his ties to the Firtash legal team, Giuliani wrote in a text message to TIME on Tuesday: “I do not represent Mr. Firtash and I have never met him.” He did not reply to requests for further comment.

Over the last two months, a TIME investigation has traced some of Giuliani’s claims about Biden and Mueller to a troubling relationship, one in which a foreigner wanted by the U.S. government on corruption charges has taken steps, as part of his own legal strategy, that are helping the American President attack his most prominent critics.

This alignment of interests has taken shape at the same time, and with many of the same goals and actors, as the parallel effort by Trump and Giuliani to pressure Ukraine into investigating Biden’s family. The effort in Ukraine was brought to light in September in a complaint from an intelligence-community whistleblower. It is now the subject of an impeachment inquiry in Congress into alleged abuse of office by President Trump.

None of the inquiry’s public proceedings so far have mentioned the assistance that Firtash’s lawyers have provided to Giuliani. While they have said some documents from the Firtash case would be useful to Trump as a defense against his critics, the lawyers told TIME this summer that the purpose of the documents is to prove their client’s innocence. Firtash’s legal team has not responded since September to numerous requests for comment about their relationship with Giuliani.

Firtash has established close ties to the former mayor of New York City in part by recruiting several of Giuliani’s associates. In July the oligarch hired two lawyers who have been helping Giuliani in his campaign to discredit Trump’s critics: Victoria Toensing and Joseph DiGenova, a married couple Trump considered hiring in 2018 as part of his private legal team. Best known as diehard defenders of Trump on Fox News, the couple has combed through the oligarch’s case files and used some of them in the effort to defend Trump on television and in the press.

Toensing and DiGenova then hired another Giuliani associate, Lev Parnas, to serve as their interpreter in communications with Firtash in Vienna, according to a statement the lawyers sent TIME on Oct. 11. While on his way to Vienna on Oct. 9, Parnas was arrested at Dulles Airport in Washington and charged with violating campaign finance laws. The indictment against him alleges that Parnas and his business partners secretly channeled money from an unidentified Russian donor to various political causes and candidates. Parnas has not entered a plea. His colleagues in the Firtash legal team declined to comment on the arrest.

Attorney Kevin Downing, right, who is representing two associates of Rudy Giuliani, Lev Parnas and Igor Fruman, walks out of a federal courthouse after a hearing in Alexandria, Va., on Oct. 10, 2019. Mark Wilson—Getty Images

In an interview with NBC News on Monday, Giuliani said he has “nothing to do with Firtash.” He also denied ever speaking to Trump about the Firtash case. “I’m not even sure the president is aware of him,” Giuliani told NBC. “I think if you asked the president ‘who is Dmitry Firtash?’ He would say ‘I don’t know.’ As far as I know, we’ve never discussed him.”

In acting for Firtash, Toensing and DiGenova’s stated aim has been to prevent their client’s extradition to the U.S. In a phone interview with TIME on July 31, soon after joining the legal team, they said he should never risk facing an American jury. “Trust me, it would be a disaster,” Toensing said. “That’s called a riverboat gamble,” added her husband.

But the lawyers spent much of the interview talking about one of their favorite topics: the alleged abuses of the special counsel’s office. They claimed that one of Mueller’s top deputies in the special counsel investigation, Andrew Weissmann, offered to drop the bribery case against Firtash in 2017 in exchange for testimony that could be damaging to President Trump. This, they claimed, would amount to suborning perjury.

They declined to provide documents to back up those claims. In a piece published on July 22, John Solomon, a columnist for the Hill, cited documents from the Firtash legal team to suggest that Weissmann’s attempts to turn Firtash were “wrapped with complexity and intrigue far beyond the normal federal case.”

Rudy Giuliani, a personal lawyer for President Trump, appears on "Meet the Press" in Washington, D.C., on April 21, 2019. William B. Plowman—NBC NewsWire/Getty Images

Weissmann, now a fellow at New York University’s law school, did not respond to emails seeking comment. During his testimony before Congress in July, Mueller bristled at Republican attempts to question Weissmann’s integrity, saying he was “one of the more talented attorneys we have on board.”

Documents from the Firtash case have become even more useful to Giuliani and Trump as they roll out their response to the impeachment inquiry. At the center of Giuliani’s counterattack so far is the affidavit signed by Shokin, Ukraine’s former prosecutor general, which alleges that Biden caused Shokin’s dismissal in order to stop a corruption probe into Burisma, a Ukrainian gas company. Biden’s son Hunter sat on the board of that company for about five years, reportedly earning $50,000 a month.

“I was forced to leave office, under direct and intense pressure from Joe Biden and the U.S. Administration,” in order to stop that investigation, Shokin said in the affidavit, which was notarized in Kiev on Sept. 4.

These claims have not stood up to scrutiny. Officials in the U.S. and Ukraine, as well as independent experts and investigative journalists, have said Shokin was fired because of his lax approach to fighting corruption. Shokin’s successor as prosecutor general, Yuri Lutsenko, has also said there is no evidence of wrongdoing by the Bidens in Ukraine.

But Giuliani’s defense of Trump amid the impeachment inquiry has relied heavily on the statement that Firtash’s legal team obtained from Shokin. After reading some of its claims against Biden during an appearance on ABC in late September, Giuliani exclaimed, “That’s under oath!”

Though their interests have aligned in recent months, Firtash and Giuliani come from starkly different backgrounds. The former mayor built his reputation in the 1990s fighting the Italian mafia in New York City. At around the same time, the tycoon was coming up through a business environment in Eastern Europe plagued by organized crime.

By the time the Department of Justice publicly referred to him in 2017 as a senior associate of the Russian mob, Firtash had been under investigation in the U.S. for more than a decade, according to interviews with his investigators.

His alleged ties to the Russian mafia go back to the early 2000s, when his work in the gas trade brought him into contact with Semyon Mogilevich, one of the most notorious leaders in the world of Russian organized crime. As Firtash later told the U.S. Ambassador to Ukraine, “he needed, and received, permission from Mogilevich when he established various businesses,” according to a U.S. embassy cable published in 2010 by Wikileaks.

In an interview with TIME in 2017, Firtash confirmed that he knows Mogilevich, but denied ever doing business with him. “He was never my partner,” he said. “He’s Ukrainian… Half the country knows him. So what? Knowing him doesn’t mean answering for him.”

By the mid-2000s, Firtash had established himself as a partner to the Kremlin in the European gas trade. With the approval of Russian President Vladimir Putin, his company had won exclusive rights to buy natural gas from Russia and resell it in Ukraine. Firtash owned about half of the company, while Gazprom, the Russian state gas monopoly, owned the other half. The arrangement made Firtash a billionaire.

With additional loans from Russian state banks, Firtash then bought up factories across Ukraine, especially in the chemicals and fertilizer industries, which helped make him an important powerbroker. In the presidential elections of 2010, he backed the Kremlin’s preferred candidate, Viktor Yanukovych, and urged his factory bosses across the country to help get out the vote. “People weren’t voting for him,” Firtash recalled of those elections in his interview with TIME. “They were voting for us. They know that politicians come and go. But we are still there with our businesses.”

Working alongside Firtash in that campaign was the American political operative Paul Manafort, who helped engineer the Yanukovych victory. As the elections approached, Firtash and Manafort also pursued some business deals on the side. They discussed a plan in 2008 to buy the Drake Hotel in Manhattan in partnership with Brad Zackson, the real estate broker for Fred Trump, the President’s father. But the deal fell through, Firtash says, because it was too much of a distraction. “I thought, America is far away,” he says. “It’s not ours. We’re busy over here.”

Former Trump campaign chairman Paul Manafort leaves his arraignment in Manhattan Criminal Court on June 27, 2019. Yana Paskova—Getty Images

During the Yanukovych presidency, Firtash expanded his business empire, buying up control of lucrative gas distribution and storage companies in many parts of Ukraine. But his luck began to run out in February 2014, when violent street protests forced President Yanukovych to flee to Russia.

A month later, Firtash was arrested near his mansion in Vienna on an arrest warrant issued by the FBI. The warrant accused him of organizing a scheme to bribe officials in India for the right to mine titanium. Because some of the metal was to be sold to a Chicago-based company, the District Attorney in that city claimed jurisdiction in the case under a law known as the Foreign Corrupt Practices Act.

Firtash has insisted the charges are politically motivated, part of an American effort to keep him out of Ukrainian politics. Since he was released on bail in Vienna in 2014–after paying a bond of $174 million–Firtash hired a formidable team of lawyers to stop his extradition from Vienna to Chicago. Among them is Michael Chertoff, the former U.S. Secretary of Homeland Security, as well as a former Austrian Justice Minister. Perhaps the most outspoken member of the legal team has been Lanny Davis, the former counsel to President Bill Clinton.

Over the last five years, this team managed to slow the extradition process, but could not stop it. The case appeared to come to a head in early June, when Firtash’s chief attorney in Chicago, Dan Webb, filed a motion warning that his client could be extradited in a matter of weeks.

Firtash’s lawyers, who declined at the time to speak on the record about their legal strategy, told TIME in June that the extradition looked imminent, and they were preparing to defend Firtash before a jury in Chicago. They also said, however, that they were ready to produce evidence that would embarrass officials from the Obama Administration. “This will be very tough against the previous Administration,” one of Firtash’s lawyers said at the end of June. “With the current Administration, I think they will like it.”

At around the same time, Giuliani was busy with his global quest to find dirt on Trump’s opponents. Two of his allies in the effort have been Toensing and DiGenova, his former colleagues from the Justice Department under the Reagan Administration.

Since 2017, Toensing and DiGenova have been among Trump’s most avid defenders on cable news in the fight against the Mueller investigation and other probes. Most recently, DiGenova called the impeachment inquiry “regicide by another name” during a Fox News appearance on Oct. 8, and referred to the intelligence-community whistleblowers as “suicide bombers.”

The pair have also worked closely with Giuliani in recent months. In early May, Toensing was due to join Giuliani on a trip to Kiev, where the two lawyers intended to pressure the new government in Ukraine to investigate the Biden family, according to a May 9, 2019, report in the New York Times. But the reporting about their plans caused such an uproar among Congressional Democrats that the two decided to cancel their trip.

On July 24, Firtash’s lawyers in Vienna informed TIME of a dramatic change in his legal team: Davis, the former counsel to President Clinton, would no longer be working for Firtash. “Lanny is out,” one of the lawyers wrote TIME in a text message on the night of July 24.

President Donald Trump arrives at the White House in Washington, D.C. on Sept. 26, 2019. Gabriella Demczuk for TIME

One of the reasons for his departure, according to two people close to Firtash, was that Davis had been representing Trump’s former lawyer, Michael Cohen, since July 2018. That relationship had made Davis an enemy of Trump. Advised by Davis, Cohen had agreed to cooperate with the Mueller investigation, and he gave damning testimony against the President before Congress.

It would have been difficult after that for Davis to get along with Firtash’s new lawyers, Toensing and DiGenova, who joined the legal team in late July, members of that team told TIME. (Davis did not respond to requests for comment.)

Alongside Toensing and DiGenova, another long-time Republican operative began representing Firtash in July: Mark Corallo, the former spokesman for Trump’s private defense team during the Mueller investigation.

Firtash’s representatives then began directing questions from journalists to Corallo. At the end of July, he arranged a phone interview for TIME with Toensing and DiGenova. During the conversation the lawyers seemed less interested in discussing their new client than they did attacking the Mueller investigation.

The Firtash case had given them plenty of talking points. “I’m almost done reading through the files,” Toensing said over the sound of shuffling papers. Among the most interesting things she said she had found was a set of memos written in the summer of 2017 by Webb, Firtash’s lawyer in Chicago.

The memos recounted a series of meetings that Webb had with Weissmann, the prosecutor from the special counsel’s office, Toensing said. During these meetings, Weissmann allegedly offered to drop the charges against Firtash in exchange for evidence that could link Trump’s campaign to the Kremlin, Toensing told TIME, citing the memos.

“They were willing to use anybody to do anything,” DiGenova added. Webb declined to comment.

Firtash’s legal team had been making such claims long before Toensing and DiGenova joined it. As early as December 2016, his lawyers had suggested to reporters in Vienna that the FBI was trying to turn Firtash into a cooperating witness against Trump. Firtash told TIME the following year that he had nothing to say to the FBI about the President’s alleged collusion with Russia.

“My problem is I don’t know Trump,” he said in the interview in Feb. 2017. “I know Manafort, and I’ve told you all I know about him. As for Putin, I’ve got nothing to do with him. So what can I tell them? If I knew something, maybe it would be itching to get out of me. But I don’t know these things.”

Contact us at letters@time.com.