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Lobbyist who got Trump Inaugural tickets for Ukrainian still having secret dealings with prosecutors

(CNN) Washington lobbyist W. Samuel Patten, who has been one of the most low-profile but potentially significant cooperators in the special counsel's office investigation, appears to still be involved with sensitive aspects of Robert Mueller and the Justice Department's work.

In a court filing Monday meant to update a judge on his case and whether he should proceed to sentencing, prosecutors revealed nothing. Instead, they filed the entire status update under seal, giving no public reason for keeping details of his case private.

The secret court filing Monday comes in contrast to several disclosures prosecutors previously made about Patten's admitted crimes — especially related to him procuring Trump inauguration tickets for a Ukrainian client — and the related lobbying work for Ukrainians done by former Trump campaign chairman Paul Manafort.

Patten previously admitted to procuring Trump inauguration tickets illegally for a Ukrainian oligarch and a Russian closely associated with Paul Manafort. Patten was a corporate lobbyist in business with the former Trump campaign chairman's longtime Russian associate Konstantin Kilimnik, whom the Mueller team has asked about in recent months and accused of having ties to the Russian intelligence group that allegedly hacked the Democrats in 2016.

Patten agreed to cooperate with the Mueller investigation and other Justice Department actions before Manafort pleaded guilty to criminal charges in September. Manafort had been Mueller's target for almost a year before his plea deal — and the Mueller team initially charged him with a host of financial crimes and foreign lobbying violations. A jury found Manafort guilty of tax and bank fraud related to his Ukrainian lobbying proceeds, then Manafort flipped and agreed to help prosecutors in September to avoid a second trial related to his foreign lobbying operation.

Patten was lined up by prosecutors as a person involved in that planned second trial against Manafort.

Typically, in a plea deal such as Patten's, once prosecutors no longer need his cooperation for an upcoming trial or to put pressure on a criminal target, they would move the case to the sentencing phase. No date has been set yet by the court for Patten's sentencing, and it's still not determined when that process would even begin.

In the two-sentence filing Monday, prosecutors gave public notice that they and Patten's legal team submitted the status report to the court under seal.

The DC US Attorney's Office filed the charge against Patten in August, after the Senate Intelligence Committee referred him to the Justice Department. As part of his plea, he admitted to lying to the Senate committee about the inauguration payment. He also admitted to failing to register as a foreign lobbyist for the Ukrainian opposition party, which including a prominent oligarch. Some of his work for the Ukrainian oligarch related to the Trump inauguration, when Patten funneled $50,000 of a Ukrainian oligarch's money to Trump's Presidential Inaugural Committee so Patten's group could secure four inauguration tickets.

His case was the first time the Justice Department publicly charged a person for helping a foreigner secretly funnel money into a Trump political event.

Even at Patten's plea hearing, Mueller's team was involved. Several members of the Mueller unit attended the plea hearing, and Patten's cooperation agreement is with both the DC US Attorney's Office and the special counsel's office. The DC US Attorney's Office is working with Mueller on several other criminal cases.