Roger Stone, the longtime adviser of former US President Donald Trump, was on Capitol Hill Friday before the January 6 committee where he refused to answer any questions, US media reported.
After his 90-minute, closed-door appearance, Stone told reporters he had invoked his Fifth Amendment right in response to every question.
Under the US Constitution, those called to testify in a federal proceeding can invoke what is known as their Fifth Amendment right against self-incrimination rather than answer questions that could put them in legal difficulty.
"I question the legitimacy of this inquiry," Stone said, lashing out at Democrats. He also disavowed knowledge of events that day, calling them "illegal and politically counter-productive."
Stone was issued a subpoena by the committee on November 22. It sought his testimony with regards to his appearances at several pro-Trump rallies in Washington, DC, on January 5, a day prior to the storming of the US Capitol.
Members of a far-right, anti-government militia known as the Oath Keepers were responsible for Stone's security on January 5 and the day of the insurrection. Members of the Oath Keepers are facing federal charges connected to the US Capitol riot.
On January 6, Trump's supporters attempted to disrupt the certification of US President Joe Biden's victory in the 2020 election by storming the US Capitol and disrupting that procedure.
The Congressional committee examining the events of that day is looking into the role Trump and his inner circle may have played.
A longtime Trump adviser, Stone was previously convicted of obstruction of justice and witness tampering by a federal jury in Washington during the special counsel's investigation led by Robert Mueller into Russian interference in the 2016 US presidential election. Stone was pardoned by Trump last December.
Two other high-profile witnesses, former Trump lawyer John Eastman and Trump-era senior Justice Department official Jeffrey Clark, have suggested they will respond to the subpoenas they received from the January 6 committee as Roger Stone has.
Several people in Trump's inner circle have refused to answer any questions from the committee. Both former campaign manager and political advisor Steve Bannon and former White House chief of staff Mark Meadows have been held in contempt of Congress.
Around 300 people have been interviewed to date by the January 6 committee. Over 700 people face federal criminal charges related to their actions in and around the US Capitol on January 6.