The police officer accused of the manslaughter of Ian Tomlinson has told a court he believed the 47-year-old was being deliberately obstructive when he hit him with a baton and pushed him to the ground.
Pc Simon Harwood, 45, told Southwark Crown Court Mr Tomlinson looked as if he "wanted" officers to move him away.
Harwood hit Mr Tomlinson with his baton and shoved him to the ground near the Royal Exchange Buildings in the City of London during the G20 protests in April 2009.
Mr Tomlinson, who was an alcoholic and slept rough for a number of years, walked around 75 yards before he collapsed and later died.
Harwood denies manslaughter on the grounds that he used reasonable force.
Giving evidence, he said he thought Mr Tomlinson was deliberately obstructing the police.
"I believed he was doing it on purpose. From what I saw he looked like he wasn't going to move and was looking at the police as though he wanted them to move him away."
He said he pushed the father-of-nine, who was walking away from a police line at the time, "firmly" after the baton strike but did not mean to push him over.
Harwood told the court that before coming across Mr Tomlinson he thought the protesters were targeting him after he tried to arrest a man for scrawling graffiti on a police carrier.
"They seemed to be goading me and shouting at me, pointing their fingers at me," he said.