By Katelyn Polantz

WASHINGTON (CNN) – Special counsel Robert Mueller has filed a charge against a lawyer for lying to investigators about his interaction with former Trump campaign aide Rick Gates in September 2016.

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Alex Van Der Zwaan is expected to plead guilty Tuesday afternoon. The filing is further evidence of Mueller’s investigation of former Trump campaign chairman Paul Manafort and Gates and their work for Russian-allied clients.

Van Der Zwaan is also accused of lying about the failure to turn over an email communication to the special counsel’s office. He was speaking with investigators about his work with Skadden Arps in 2012, when Manafort arranged for the firm to be hired by the Ukrainian Minister of Justice to prepare a report on the trial of Yulia Tymoshenko.

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She is one of the top political rivals of former Ukrainian President Viktor Yanukovych, who hired Manafort and Gates as political consultants for more than a decade.

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After Yankovych narrowly defeated Tymoshenko in the 2010 presidential election, she was jailed on charges of corruption that were seen by many as being politically motivated. Skadden produced a report that said the process was legal. She was freed after Yankovych’s ouster in 2014.

Van Der Zwaan has a plea hearing scheduled for Tuesday afternoon at US District Court in Washington, DC.

Gates close to plea deal

Gates is finalizing a plea deal with Mueller’s office, indicating he’s poised to cooperate in the investigation, sources familiar with the case told CNN last week.

He has already spoken to Mueller’s team about his case and has been in plea negotiations for about a month. His cooperation could be another building block for Mueller in a possible case against President Donald Trump or key members of his team.

Once a plea deal is in place, Gates would become the third known cooperator in Mueller’s sprawling probe into Russian interference in the 2016 presidential election. It would also increase the pressure to cooperate on Manafort, who has pleaded not guilty to Mueller’s indictment and is preparing for a trial on alleged financial crimes unrelated to the campaign. Gates pleaded not guilty on October 30 alongside Manafort.

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