UPDATE: Special counsel Robert Mueller has filed a new charge against an attorney — the son-in-law of a Ukranian-Russian oligarch named in the controversial Donald Trump dossier — who is accused of lying to investigators in the Russia investigation.

Alex van der Zwaan was charged with making false statements about his communications with former Trump campaign aide Rick Gates, according to a court document obtained by NBC News. He is expected to plead guilty Tuesday afternoon.

READ MORE | Takeaways from Mueller's Russian meddling indictment

Gates and his longtime business associate, former Trump campaign chief Paul Manafort, were indicted in October on charges of money laundering, conspiracy and other offenses tied to their lobbying on behalf of Ukrainian political figures.

Van der Zwann worked in the London office of international law firm Skadden, Arps, Slate Meagher & Flom for a decade. The firm said it fired him last year and has been cooperating with Mueller, who is investigating Russian interference in the 2016 election and possible links to the Trump campaign.

Van der Zwaan's former employer, Skadden Arps, worked on a report on behalf of the Ukrainian government that critics said sought to justify the false imprisonment of Ukraine's former prime minister, Yulia Tymoshenko. The watchdog group Freedom House criticized the report's findings as "utterly baffling."

Manafort and Gates were also working on behalf of Tymoshenko's rivals, including ousted president Viktor Yanukovych. The New York Times reported in September that Manafort arranged for Skadden to do the work — and that prosecutors were asking questions about it.

The lawyer's father-in-law is German Khan, a billionaire who filed a libel suit in October against Fusion GPS, the investigation firm behind a partly unsubstantiated intelligence dossier that alleged Donald Trump's campaign colluded with the Russians.

Van der Zwaan married Eva Khan, an art critic and debutante, last year in a lavish wedding at the Luton Hoo estate in the English countryside, where "Four Weddings and a Funeral" and "Vanity Fair" were filmed, according to the BigBagBlog.

According to the charging documents, Alex van der Zwaan was questioned in November and claimed that his last communication with Gates was an "innocuous" text message in mid-August 2016. He also said his last communication with someone described only as Person A was in 2014 and that he did not know why a 2016 email exchange with Person A was not turned over to Mueller, the document alleges.

But, according to the prosecutors, van der Zwaan spoke with both Gates and Person A in September 2016 regarding the Tymoshenko report, surreptitiously recorded the calls and deleted the email in question.

The charge against van der Zwaan was announced just days after Mueller indicted 13 Russian nationals accused of interfering in the 2016 presidential election. Trump attorney Ty Cobb declined to comment saying the case, like the Manafort and Gates indictments, is not related in any way to the White House.

If van der Zwaan pleads guilty, he will be the fourth person to cut a deal with Mueller. The others are:

  • Mike Flynn: Trump's short-tenured national security advisor pleaded guilty in December to a charge of making false statements to the FBI about his communications with Russia after the election but before the inauguration — allegedly made at the urging of Trump's son-in-law Jared Kushner and Flynn's former deputy, K.T. McFarland.
  • George Papadopoulos: The former Trump campaign advisor secretly pleaded guilty in October to lying to federal agents about his contacts with Kremlin-connected Russians — communications that Manafort was allegedly knew about.
  • Richard Pinedo: The California man pleaded guilty this month to selling bank account and other stolen identify information to the Russian defendants accused of interfering in the election.