Seven policemen have been convicted of attacking activist Ken Tsang during the 2014 Umbrella Movement.
The District Court found them guilty of assault occasioning actual bodily harm, footage of which was captured by local news media.
They will be sentenced on Friday and could be jailed for up to three years.
Judge David Dufton handed down his verdict in a courtroom packed with supporters of both Tsang and the seven police officers.
The defendants were dressed in matching suits and ties, as they had been throughout the trial.
They had together stood accused of causing grievous bodily harm with intent. The officers' supporters broke into applause when Dufton read out his decision on that joint charge -- not guilty.
But they were quickly shushed and the court fell silent as the judge then pronounced the seven guilty of the lesser charge of assault occasioning actual bodily harm.
Detective Constable Chan Siu-tan was also found guilty of an additional charge of common assault, for slapping Tsang twice at Central Police Station.
Dufton said video and photos from the early hours of October 15, 2014 accurately depicted the assault as it happened. The evidence showed Tsang pouring liquid onto police officers on Lung Wo Road, as they attempted to clear protesters from around Tamar Park.
The activist was arrested by uniformed police, zip-tied and handed over to the defendants. But they carried him face down to a place off Tamar Park instead of coaches destined for Central Police Station, like for others arrested that morning.
The judge said the only inference that could be drawn was that Tsang was carried away to be assaulted.
He said the officers dumped him on the ground and set about kicking and stamping on him, leaving him with injuries to his face, neck, chest and back. Footage of the assault was broadcast on news channels in Hong Kong later that morning.
The two senior officers among the seven – Chief Inspector Wong Cho-shing and Senior Inspector Lau Cheuk-ngai – did not take part in the actual assault but "encouraged and supported it".
However, the judge ruled that the injuries Tsang sustained in the dimly lit corner of Tamar Park did not amount to grievous bodily harm. Instead, he found the officers guilty of the lesser charge of assault occasioning actual bodily harm, which carries a maximum sentence of three years imprisonment.
"Every police officer has a duty to intervene to prevent the commission of a crime, even by fellow police officers. A police officer’s duty is to keep the peace", Dufton said.
"If a police officer stands by and watches his colleague beat up a suspected person, his failure to intervene is evidence of encouragement to carry out the assault", the judge added.
In mitigation, defence lawyers spoke about the unique pressure created by the 2014 protests – how officers needed to work long shifts, and faced verbal and physical abuse.
One of the lawyers told the court that "human frailty resulted in the transgression of seven devoted officers".
Responding to the judge's ruling, Tsang said he would need time to study the verdicts.
A police spokesman said they will study the judgment.
Last updated: 2017-02-14 HKT 21:27
Seven policemen guilty of attacking Ken Tsang
2017-02-14 HKT 09:52
2018-03-23 HKT 13:02
2018-03-16 HKT 11:07
2018-03-08 HKT 17:51
2018-02-15 HKT 10:40
2018-02-12 HKT 13:30
2018-02-01 HKT 17:10
2018-01-18 HKT 18:01
2017-11-23 HKT 12:34
2017-07-14 HKT 15:30
2017-07-06 HKT 17:06
2017-06-28 HKT 12:35
2017-04-20 HKT 11:59
2017-03-21 HKT 09:51
2017-03-20 HKT 19:56