A retired New York City policeman charged with assault in the US Capitol riot testified on Thursday that he was acting in self-defence when he struck a Washington officer with a flag stick and tackled him.
Thomas Webster, 56, testified that he drove to Washington to join a peaceful protest by supporters of then-president Donald Trump.
Mr Webster is trying to become the first participant in the January 6 riot to secure an acquittal in a jury trial.
"That officer incited me," he told jurors when asked why he struck a Washington Metropolitan Police officer.
"I felt like I was dealing with a rogue cop."
Mr Webster alleged the officer had escalated the situation by punching him in the face.
Of the four accused Capitol rioters to face a jury so far, Mr Webster is the first to claim he was acting in self-defence.
He served in the US Marine Corps before spending about 20 years with the New York Police Department.
Prosecutors have rejected Mr Webster's defence and portrayed the District of Columbia police officer, Noah Rathbun, as the victim in the altercation.
Prosecutors said Mr Rathbun made physical contact with Mr Webster to create distance between the two men, who were on opposite sides of a police barricade eventually overrun by Trump supporters.
US District Judge Amit Mehta has expressed scepticism at Mr Webster's self-defence claim.
"You were a police officer. You should know better," the judge said during a court hearing in June.
About 800 people are charged with a role in the Capitol riot, which disrupted a joint session of Congress that was to certify Joe Biden's presidential election victory, and sent legislators scrambling for safety.
About 250 have pleaded guilty so far.
Prosecutors have obtained convictions in all three jury trials so far, but have had a mixed record in trials decided by judges.
