An Arizona man who sported face paint, no shirt and a furry hat with horns when he joined the mob that stormed the US Capitol has pleaded guilty to a felony charge and wants to be released from jail while he awaits sentencing.

Jacob Chansley, who was widely photographed in the Senate chamber with a flagpole topped with a spear, could face 41 to 51 months in prison under sentencing guidelines, a prosecutor said.

The man who called himself “QAnon Shaman” has been jailed for nearly eight months since his arrest.

Before entering the plea, Chansley was found by a judge to be mentally competent after having been transferred to a Colorado facility for a mental health evaluation.

His lawyer Albert Watkins said the solitary confinement that Chansley faced for most of his time in jail has had an adverse effect on his mental health and that his time in Colorado helped him regain his sharpness.

“I am very appreciative for the court’s willingness to have my mental vulnerabilities examined,” Chansley said before pleading guilty to a charge of obstructing an official proceeding.

US District Judge Royce Lamberth is considering Chansley’s request to be released from jail while he awaits sentencing, which is set for November 17.

Chansley acknowledged in a court record to being one of the first 30 pro-Trump rioters to stream into the Capitol building.

He riled up the crowd with a bullhorn as officers tried to control them, posed for photos, profanely referred to then-vice president Mike Pence as a traitor while in the Senate.

He wrote a note to Pence saying: “It’s only a matter of time, justice is coming.” He also made a social media post in November in which he promoted hangings for traitors.

The image of Chansley with his face painted like the American flag, wearing a bear skin head dress and looking as if he were howling was one of the first striking images to emerge from the riot.

Chansley is among roughly 600 people charged in the riot that forced lawmakers into hiding as they were meeting to certify President Joe Biden’s Electoral College victory.

Fifty others have pleaded guilty, mostly to misdemeanour charges of demonstrating in the Capitol.