A former lawyer for a major U.S. law firm pleaded guilty Tuesday in federal court in Washington D.C., to lying to federal authorities in a case that is part of Special Counsel Robert Mueller’s wide-ranging Russia probe.

The guilty plea by Alex van der Zwaan, who worked at the firm Skadden Arps Slate Meagher & Flom LLC until he was terminated in November, came as part of a plea agreement between Mueller’s team. The case is being overseen by U.S. District Judge Amy Berman Jackson, who is also overseeing Mueller’s cases against former Trump campaign aides Paul Manafort and Rick Gates.

Manafort, a former Trump campaign chairman, and Gates, his deputy who also worked for the campaign, pleaded not guilty last October to charges brought by Mueller related to their work in Ukraine for a pro-Russian political party. Skadden was recruited by Manafort to write a 2012 report justifying the Ukrainian government’s prosecution and conviction of Yulia Tymoshenko, a political rival of Viktor Yanukovych, whom Manafort was advising.

Van der Zwaan pleaded guilty to lying to investigators about his communications with Rick Gates and an unidentified third person known as “person A”.

Van der Zwaan was questioned by investigators on Nov. 3, 2017, about conversations he had with Gates and a “Person A” in the fall of 2016.

At Tuesday’s plea hearing, Andrew Weissmann, a prosecutor on Mueller’s team, broadly described van der Zwaan’s communications with Gates and “Person A,” as well as what he told federal investigators about those communications last year.

“Person A” was described by Weissmann as someone who spoke Russian and who was located in Ukraine. Gates, “Person A” and van der Zwaan worked together on the rollout of the 2012 Tymoshenko report, Weissmann said.

FBI agents and prosecutors interviewed van der Zwaan under oath at the special counsel’s office in November, as part of Mueller’s investigation into Manafort and Gates’ alleged Foreign Agents Registration Act violations. Van der Zwaan told them that the most recent communication he had with Gates was an “innocuous” conversation in August 2016 and that he hadn’t communicated with “Person A” since 2014, when in fact, according to Weissmann he spoke to them both in September 2016.

A statement of offense that was released to the public after the hearing said that Gates called van der Zwaan in September 2016 to tell him to contact “Person A.” Gates also sent the lawyer documents that included a “preliminary criminal complaint in Ukraine,” using the encryption service Viber, according to the court filing. Van der Zwaan called “Person A” to discuss in Russian the potential for charges to be brought against Skadden and Manafort — a call that the lawyer recorded, according to the court filing. He then called a senior partner who worked on the 2012 report — a call he “partially recorded,” according to the filings — and also called Gates. Van der Zwaan recorded the Gates call and took notes on all of the calls, according to the statement of offense.

During his November 2016 interview, Van der Zwaan was also asked about an email “Person A” sent him in Russian, that, according to Weissmann, was not handed over to his law firm to produce for Mueller’s team. Van der Zwaan told investigators he did not know why that email wasn’t produced and that he didn’t respond to it, according to Weissmman. Van der Zwaan “knew full well” that he had not produced it and that he destroyed that and other emails, Weissmann said.

Van der Zwaan is 33 years old and the son-in-law of Ukrainian-Russian billionaire German Khan. Born in Brussels, he obtained a law degree in Britain and is now a Dutch citizen.

As part of the plea hearing, van der Zwaan indicated that he and Mueller had come to an agreement on recommending that he face zero to six months of jail time, and a fine between $500-$9,500 as part of his plea. Judge Amy Berman Jackson reminded him that there’s no guarantee that that will be his ultimate sentence.

It was also revealed during the hearing the van der Zwaan’s wife was dealing with a difficult pregnancy, with his attorneys asking that they expedite his sentencing hearing. Jackson set the sentencing hearing for the morning of April 3. In the meantime, his travel is restricted to the Washington, D.C.-area and to Manhattan, where his lawyers are located. His passport has been handed over to the FBI, and he will need to get court approval for any other travel within the continental United States.