Michael Cohen has been making the rounds since his late-August guilty plea in federal court, offering himself up to a number of offices that are investigating him or other aspects of the Trump orbit.
And on Friday, Cohen set off fresh speculation when he made an unexpected appearance in Manhattan federal court, where defendants typically sit for interviews before their sentencing.
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But it's not clear what President Donald Trump's former personal attorney can provide prosecutors or others probing these matters -- and it's uncertain Cohen will receive any benefit in return.
He has met with prosecutors from the office of special counsel Robert Mueller, where he provided "critical information" to that investigation, an attorney and adviser to Cohen, Lanny Davis, said Thursday night on Twitter.
Prosecutors from the US Attorney's Office for the Southern District of New York, who charged Cohen in August, had been seeking to arrange for him to sit down with them, according to a person with knowledge of the matter, and former prosecutors familiar with the process said it was likely that those from the US attorney's office would have participated in Cohen's sessions with the Mueller team, given that the two sets of prosecutors have different investigative interests and different areas of expertise.
Mueller's team has been probing Trump and his campaign's relationship to Russia, while federal prosecutors in New York are now examining possible campaign finance violations by others within the Trump Organization.
Cohen pleaded guilty to eight counts, including tax evasion, making false statements to a bank and campaign finance violations. He is scheduled to be sentenced in December, leaving a window in which he can try to aid investigators in an effort to earn a reduced sentence.
Since he doesn't have a cooperation agreement, which dictates that a defendant provide any information requested by the government, he isn't required to answer all of prosecutors' questions when he meets with investigators, and he may decline to answer those that could further implicate him.
Still, there are several topics on which Cohen could aid prosecutors and perhaps win himself a lighter sentence.
He was deeply involved in Trump's efforts to build a Trump Tower in Moscow in 2015, CNN has reported -- an effort that Trump never publicly disclosed during the presidential campaign. Investigators working for the special counsel have examined whether Trump had any business dealings that could have put him or his associates in a compromising position with Russia.
And Cohen has had other Russian contacts. A Russian oligarch, Viktor Vekselberg, who was questioned by the special counsel's office and sanctioned by the US, is connected to a company, Columbus Nova, that gave Cohen a $580,000 consulting contract starting in January 2017, CNN has reported. That same month, Vekselberg visited Cohen in Trump Tower during the presidential transition, CNN has reported.
While the US attorney's office had been investigating Cohen for possible illegal lobbying, it declined to pursue such charges after it failed to find sufficient evidence that he had, in fact, contacted government officials on behalf of any of his clients, according to a person familiar with the matter. But Cohen's contacts with Russians could still be of interest to Mueller prosecutors.
The special counsel may also ask Cohen what he knows about the infamous Trump-Russia dossier and whether he can confirm any of the details in it. The collection of secret memos was written by a former British spy, Christopher Steele, throughout 2016, and it alleged that there was widespread collusion between the Trump campaign and the Russian government and Cohen had played a leading role in the conspiracy. Cohen has denied these allegations, including in testimony to congressional investigators.
Beyond conversations with the Mueller team, Cohen has taken steps in recent weeks to comply with New York state inquiries into him or related to entities with which he has been involved: the Trump Foundation and the Trump Organization.
Last week, Cohen and his attorney Guy Petrillo met with investigators and lawyers at the New York State Department of Taxation and Finance, according to a department spokesman. That office, CNN has reported, is conducting an inquiry into possible tax fraud at the Trump Organization based on evidence included in the August charges against Cohen from federal prosecutors. It is also examining whether the company kept accurate books and records, as the failure to do so is a state crime, CNN has reported.
Cohen was also in contact with the New York state attorney general's office shortly after he pleaded guilty in federal court, according to a person familiar with the matter. That office has been coordinating its investigation with the US attorney's office, which in recent weeks has urged state offices to avoid taking certain investigative steps while their federal case against Cohen proceeds, CNN reported.