WASHINGTON — A London-based lawyer was ordered to serve 30 days in prison after a federal judge Tuesday handed down the first sentence in Special Counsel Robert Mueller’s investigation of alleged Russian interference in the 2016 U.S. presidential election.

Alex van der Zwaan, 33, a son-in-law of a prominent Russian-based banker, pleaded guilty Feb. 20 to lying to the FBI about his contacts in September and October 2016 with a business associate of onetime Trump campaign chairman Paul Manafort and with Manafort’s deputy, former Trump aide Rick Gates. Prosecutors said van der Zwaan also destroyed emails the special counsel had requested.

According to prosecutors, van der Zwaan, who is a Dutch citizen, said he had been told by Gates that the Manafort associate had been an officer with the Russian military intelligence service. Van der Zwaan turned over secret recordings to Mueller’s investigators that he had made of his conversations with Gates, the associate, and a senior partner at his law firm.

In court Tuesday, van der Zwaan said, “What I did was wrong. I apologize to the court for my conduct. I apologize to my wife and to my family for the pain I have caused.”

While van der Zwaan is not a central figure in the investigation, filings in his case illustrated Mueller’s continuing interest in Manafort and Gates’ actions through Donald Trump’s presidential campaign.

Van der Zwaan was an attorney in the London office of Skadden, Arps, Slate, Meagher & Flom from 2007 to 2017, when the firm worked with Manafort during a decade when he served as a political consultant in Ukraine.

Manafort, 68, has pleaded not guilty to conspiracy, money laundering, and tax and bank fraud charges related to his lobbying work for a pro-Russian political party in Ukraine and former Ukrainian President Viktor Yanukovych. He has asked a judge to toss out charges, saying prosecutors are pursuing conduct that predate his work for Trump.

Gates, 45, who was deputy campaign manager for Trump and worked with Manafort in Ukraine, pleaded guilty Feb. 23 to conspiracy and lying to the FBI in a cooperation deal with Mueller’s probe.

Van der Zwaan admitted lying and withholding documents about information prosecutors said was “pertinent” to their investigation: that Gates had been in direct contact during Trump’s presidential run with the Manafort associate, identified in court documents as “Person A,” an individual who “has ties to a Russian intelligence service and had such ties in 2016.”

Prosecutors said when van der Zwaan was interviewed by the FBI in November, he told investigators Gates had informed him that Person A was a former officer of the Russian military intelligence service known as the GRU.

Prosecutors made the allegation without naming the Manafort associate but described his role with Manafort in detail. The description matches Konstantin Kilimnik, the Russian manager of Manafort’s lobbying office in the Ukrainian capital, Kiev.

Kilimnik ran Manafort’s office in Kiev during the 10 years he did consulting work there, The Post reported in 2017.

Kilimnik has previously denied intelligence ties, telling The Washington Post in a statement in June that he has “no relation to the Russian or any other intelligence service.”

A spokesman for Manafort, who is under a court gag order, has previously declined to comment about the van der Zwaan filings.

Van der Zwaan faced a recommended sentence ranging from zero to six months in prison and asked for no prison time for one count of lying to investigators, a felony. He made his false statements to Mueller’s investigation on Nov. 3, and Skadden said it terminated him that month.

He also is married to the daughter of billionaire German Khan who owns the Alfa Group, Russia’s largest financial and industrial investment group.

Van der Zwaan attorney William Schwartz said that the defendant should not be punished because of who his family is, and deserved credit for the loss of his career, suffering of his wife, who is expecting the couple’s first child in August in a difficult pregnancy, and for turning over recorded conversations and other evidence of his guilt.

“It is unusual conduct to make a false statement, and then immediately provide proof of a false statement,” Schwartz said, saying for if it were another defendant those tapes “could have found their way to the bottom of the Thames” River in London.

U.S. District Judge Amy Berman Jackson acknowledged van der Zwaan’s character and willingness to turn over evidence of his crimes, but said given his means that allowing the defendant to “pay a fine at the door and walk away would not send a message of deterrence. It would do the opposite,” Jackson said.

“It is a message that needs to be sent, particularly because you are an attorney,” she said.

Jackson said she did not know if van der Zwaan was motivated to join Manafort and Gates for excitement, the money, or was engaged in a deeper “coverup,” but that in lying “he put his own interests ahead of the interests of justice” in an investigation of national and international importance into whether the U.S. democratic process was corrupted.

Manafort has acknowledged staying in frequent contact with Kilimnik during the time he worked for Trump’s campaign. He has said he met with Kilimnik in person in May 2016 and again in New York City in August 2016, about two weeks before Manafort resigned as Trump’s campaign chairman.

A Manafort spokesman expressed confidence in June that investigators would ultimately conclude Manafort’s interactions with Kilimnik were “perfectly permissible and not in furtherance of some conspiracy.”

During his August 2016 meeting with Kilimnik, Manafort has said he and his longtime Kiev office manager discussed, among other topics, the ongoing campaign, including the hacking of Democratic National Committee emails. Stolen DNC emails had been released by WikiLeaks the previous month, and the hack was widely suspected to be the work of Russia.

During Kilimnik’s time working for Manafort in Kiev, he was a liaison for Manafort to the Russian aluminum magnate Oleg Deripaska, with whom Manafort had done business. Emails previously described to The Post show Manafort asked Kilimnik during the campaign to offer Deripaska “private briefings” about Trump’s effort. A Deripaska spokeswoman has said the billionaire, a close ally of Russian President Vladimir Putin, was not offered and did not receive briefings.

Van der Zwaan, who joined Skadden in 2007, when he was about 24, played a role at the firm in complex international litigation and government investigations that belied his junior status, a fact his lawyers attributed to his international upbringing and his command of French, Russian and English as well as Dutch.

Van der Zwaan’s archived biography at the law firm stated that he represented Millhouse Capital and Evraz Holding, the private London investment firm and Russian steel and mining conglomerate owned by Russian billionaire Roman Abramovich, and defended Ukrainian banking, energy and mining oligarch Gennadiy Bogolyubov against separate claims by a fellow Ukrainian billionaire, Viktor Pinchuk, and a Russian oil company, TatNeft.

Van der Zwaan last June married Eva Khan, the daughter of Khan. The couple is expecting their first child in August after a “difficult” pregnancy, a factor his defense argued in requesting leniency from the court.

Prosecutors alleged that van der Zwaan falsely told federal investigators that he last communicated with Gates in mid-August 2016 through an innocuous text message.

Prosecutors said van der Zwaan was lying, and that he spoke to Gates and Person A in September 2016 using encrypted communications — conversations that he recorded, including a separate conversation he had with Gregory Craig, a Skadden senior partner overseeing work involving Manafort.

Van der Zwaan also deleted emails rather than turning them over to authorities, including one from Person A directing him to communicate using an encrypted application, and others showing he explored leaving the law firm to work directly for Gates and Manafort in about 2012 and 2013.

The subject of the recorded phone call, prosecutors said, was a 2012 report prepared by van der Zwaan’s law firm about the jailing of former Ukrainian prime minister Yulia Tymoshenko. Yanukovych had imprisoned Tymoshenko, a political rival, after a gas supply controversy in 2009 involving Russia.

The Skadden report has been controversial in Ukraine in part because its findings seemed to contradict the international community’s conclusion that Tymoshenko had been unjustly jailed.

In addition, the Ukrainian government claimed to have paid only $12,000 for the report, an amount that put it just below the limit that would have required competitive bidding for the project under Ukrainian law.

Prosecutors have alleged that Manafort and Gates used an offshore account to secretly pay $4 million for the report.

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