Long-time Trump associate and former campaign adviser Roger Stone pleaded not guilty in a federal DC court on Tuesday.

Stone appeared in front of Magistrate Judge Deborah Robinson following his arrest by the FBI on Friday. Stone has been charged with obstruction of a proceeding, witness tampering and making false statements to House Representatives regarding his involvement in WikiLeaks’ publication of stolen emails related to Hillary Clinton’s 2016 presidential campaign.

Stone is the sixth Trump associate to be charged in Special Counsel Robert Mueller’s investigation, and the first to plead not guilty. In response to Stone’s arrest, the White House stated on Monday that the legal proceedings against Stone are not related to the president.

Stone’s case will be jointly tried by Special Counsel Robert Mueller’s office and the US Attorney for the District of Columbia. His first status hearing will be on Friday, February 1, before Judge Amy Berman Jackson, who is also handling Paul Manafort’s case.