Media gather in front of Rudy Giuliani's Manhattan apartment after federal investigators executed a search warrant on April 28, 2021.
Tayfun Coskun—Anadolu Agency via Getty Images
Updated: April 29, 2021 4:22 PM EDT | Originally published: April 29, 2021 4:22 PM EDT

By the time federal investigators searched the Manhattan home of Rudy Giuliani on Wednesday, they had amassed a trove of evidence from his associates in Ukraine, focusing most intently on Giuliani’s ties to Ukrainian oligarchs, three witnesses in the case told TIME.

The witnesses, who spoke on condition of anonymity, described lengthy interviews with investigators in Europe, Manhattan and Washington, starting in the fall of 2019 and continuing through February. The calls and meetings with investigators grew more frequent and “intense” after Joe Biden’s victory in last fall’s presidential election, says one of the witnesses. Two of the witnesses say they were working with Giuliani while cooperating with federal investigators.

A spokesman for the U.S. Attorney’s office in Manhattan declined to comment on the case. Giuliani did not respond to a request for comment about his former associates in Ukraine assisting federal prosecutors. In a statement released Wednesday, the former Mayor of New York City and personal lawyer for President Donald Trump called the investigation against him an “unjustified and unethical attack,” and said he “can demonstrate that his conduct as a lawyer and a citizen was absolutely legal and ethical.”

The investigation of Giuliani grew out of a federal probe into two of his associates, Lev Parnas and Igor Fruman, who were arrested in Oct. 2019 and charged with violating campaign finance law. Both men have denied the charges and are awaiting trial.

Before they were arrested, Parnas and Fruman assisted Giuliani in his quest to connect Biden, then a candidate for the Democratic presidential nomination, to alleged acts of corruption in Ukraine. Drawing on a cast of oligarchs, former prosecutors and alleged Russian agents in Ukraine, Giuliani and his allies spent more than a year trying to tarnish Biden and his son Hunter, who served on the board of a Ukrainian gas company while his father was Vice President.

The pressure campaign to coerce Ukrainian officials into providing damaging material about the Bidens ultimately resulted in Trump’s first impeachment by the House of Representatives in Dec. 2019. The impeachment inquiry found that Trump abused his office while assisting Giuliani’s mission against Biden. The Republican-controlled Senate later acquitted Trump of these charges.

While the impeachment inquiry was underway that fall, federal investigators began questioning Giuliani’s associates about the smear campaign against the Bidens in Ukraine, wanting to know “everything – every meeting, every text,” says one of people they spoke to at the time.

What interested investigators most of all was the relationship between Giuliani and the Ukrainian businessman Dmitry Firtash, who is wanted in the U.S. on corruption charges, this witness says. “The main things that interested them was: How would you assess, how would you describe, what do you know about his communication with Ukrainian oligarchs,” says this witness, who spoke repeatedly to investigators over the course of more than a year. “Firtash was of course their main focus, without a doubt.”

In a statement released on April 30, Firtash’s lawyers said the billionaire did not help Giuliani’s efforts to discredit the Biden family. “Mr. Firtash never authorized anyone on his behalf to have any involvement in an investigation about the Bidens in the Ukraine. He has said that he was ‘sucked into’ this internal U.S. fight without his will and desire. He did not provide any ‘dirt-digging efforts,'” the statement said.

As TIME reported in a previous investigation, Firtash developed close ties with Giuliani’s associates in the summer of 2019, hiring several of them to work on his legal team. Firtash’s goal was to avoid extradition to Chicago, where he faces charges related to an alleged scheme to bribe officials in India. From his home in Vienna, Firtash has denied those charges and insisted they are politically motivated.

As part of his defense, Firtash hired two lawyers in July 2019 who are close associates of Giuliani: Victoria Toensing and Joe diGenova, a married couple known for their staunch allegiance to Trump. The couple then sought Firtash’s help in their effort to discredit the Biden family.

The nexus between Giuliani, Firtash and the two U.S. lawyers with ties to the 45th President was among the issues that interested prosecutors the most, according to two of the Giuliani associates questioned by federal investigators.

On Wednesday morning, while serving a search warrant at Giuliani’s apartment in Manhattan, federal agents also arrived at Toensing and diGenova’s home outside Washington with a warrant for Toensing’s phone.

In a statement, the couple’s law firm said that Toensing was not a target of the investigation. “She has always conducted herself and her law practice according to the highest legal and ethical standards,” the statement said. “She would have been happy to turn over any relevant documents. All they had to do was ask.”

Contact us at letters@time.com.

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