The police officer accused of killing Ian Tomlinson was "making an example of him" when he struck him with a baton and pushed him to the ground, a court has heard.
Southwark Crown Court was read a statement from American businessman Christopher La Jaunie, who filmed Pc Simon Harwood hitting the 47-year-old.
He was facing away from a line of police officers when he was hit, and walked 70 metres before he collapsed and later died.
Prosecutor Mark Dennis QC read Mr La Jaunie's statement, which said: "Mr Tomlinson was not posing any threat to the officers prior to this, or aggravating them.
"I had the impression that the officer was making an example of him."
The businessman came forward with his footage after Mr Tomlinson's family appealed for information, the court heard.
Initially a pathologist found that he had died of natural causes, having suffered a heart attack, but later reports suggested internal injuries led to his death.
Mr La Jaunie said Mr Tomlinson was "bumping along" the line of officers, trying to get through.
He said: "I couldn't understand why he was getting so close to the police line. I thought they might see this as some kind of a threat.
"I didn't see him as a protester, I had the impression that he was just intoxicated and a bit out of sorts, just trying to get home."
Giuseppe Di-Cecio, who worked nearby, said Mr Tomlinson did not look like a threat to the police.
He told the court: "It was a bit harsh, what we commented at the time was that it was a bit harsh because this guy didn't look like a threat at all. He was not in a crowd, he was kind of isolated.
"He was not making physical contact with the officer who pushed him.
"Mr Tomlinson fell heavily on the ground, so we thought he might have injured himself."