Last Updated Dec 1, 2017 1:17 PM EST
Update:has pleaded guilty to lying to the FBI.
Former White House National Security Adviserwill plead guilty on Friday to one count of making false statements to the FBI. He'll appear at a federal courthouse in Washington Friday morning before U.S. District Judge Rudolph Contreras for a plea hearing.
A document filed with the court by the special counsel says that Flynn "did willfully and knowingly make materially false, fictitious and fraudulent statements and representations" to the FBI regarding his interaction with then-Russian Envoy Sergey Kislyak. In early December, after the election, he and the president's son-in-law and top adviser Jared Kushner met with Kislyak at Trump Tower. On Dec. 29, Flynn called Kislyak five times, and the two spoke about sanctions against Russia that had just been imposed by President Obama over Russia's meddling in the U.S. 2016 elections.
Read: Flynn plea agreement
Flynn was forced to resign in February for misleading Vice President Mike Pence and others about the content of those calls.
Flynn's legal team recently stopped cooperating with the White House, which appeared to be a sign of an impending plea deal. Previously, Flynn's lawyers had openly shared information about Special Counsel Robert Mueller's investigation with President Trump's legal team.
CBS News has confirmed that U.S. law enforcement officials have long suspected that Michael Flynn did not engage the Russian ambassador without being directed to do so. Soon after electronic intercepts picked up the conversations between Sergey Kislyak and Flynn, U.S. officials began to suspect that someone encouraged him to do it.
The lack of a Russian response to the sanctions imposed by the Obama administration stunned intelligence officials working in the Obama Administration. In an interview earlier this year former Director of National Intelligence James Clapper told CBS that the reaction was "very un-Russian-like" and "curious."
Friday's plea agreement with Flynn suggests that the Special Counsel's office views the conversation with Kislyak as an important or perhaps even a critical aspect of the overall investigation as prosecutor's try to determine who else up the Trump transition chain of command was aware of the conversations.
CBS News' Paula Reid points out that there were at least three charges Flynn could have faced, the most serious of which was a Foreign Agents Registration Act (FARA) violation -- a failure to register as a foreign agent to disclose work for a foreign government. While he was a top adviser for the Trump campaign, Flynn had a $600,000 lobbying contract with a Dutch company owned by a Turkish businessman, work that he acknowledged could help the Turkish government. He made this FARA disclosure in March, months after he'd been pushed out of the White House.
Flynn turned himself in to the FBI Friday morning. He was processed and charged and is now headed to federal court. It was done quietly and out of the view of cameras.
He has been a key figure in the federal investigation into Russian interference in the 2016 election. As lieutenant general, he was forced out out of the Obama administration as head of the Defense Intelligence Agency in August 2014. A little over a year later, in December 2015, Flynn was photographed at a gala in Moscow where he sat next to Russian President Vladimir Putin. A few months later, in February 2016, he joined the Trump presidential campaign as an adviser. Mr. Trump, when he was president-elect, announced a few weeks after the November election that Flynn had accepted the position of White House national security adviser. In December 2016, Flynn reportedly called Kislyak five times, with U.S. sanctions imposed on Russia as one issue brought up in conversations.
In January, Pence, then president-elect, appeared on CBS's "Face the Nation" and defended Flynn, saying that Flynn did not discuss sanctions with Kislyak. In February, investigators learned that Flynn did discuss U.S. sanctions on the phone with Kislyak, despite the vice president's public denial on CBS News' "Face the Nation." A source close to the vice president told CBS News that the vice president's statement was based on what Flynn personally told him. A few days later, Flynn resigned as national security adviser on Feb. 13.
A day after his resignation, Mr. Trump asked then-FBI Director James Comey to end the federal investigation into Flynn. Documented in a memo by Comey, Mr. Trump said to Comey in the meeting, "I hope you can see your way clear to letting this go, to letting Flynn go." He added, "He is a good guy, I hope you can let this go." Comey responded and agreed that Flynn "is a good guy."
Flynn's decision to plead guilty comes after Mr. Trump's former 2016 campaign chairman Paul Manafort and Rick Gates, Manafort's former business associate, were indicted in late October by a federal grand jury in the investigation into Russian meddling in the U.S. election. They pleaded not guilty in federal court.
Another Trump campaign aide, George Papadopoulos, pleaded guilty to making false statements to the FBI. His statements had to do with the nature of his relationship with "certain foreign nationals whom he understood to have close connections with senior Russian government officials."
Here is the plea document submitted to the court by the special counsel:
This is a developing story.
CBS News' Paula Reid and Jeff Pegues contributed to this report.