MOSCOW -- A court in Moscow has found Mikhail Kosenko guilty of assaulting a police officer and participating in the mass antigovernment unrest on Moscow's Bolotnaya Square in May 2012.
He was sentenced to forced treatment in a psychiatric clinic.
Kosenko suffered a head injury while serving in the Russian Army and is legally handicapped.
The judge ruled he could not be sent to prison due to his condition. Kosenko had pleaded not guilty.
Investigators say the Bolotnaya protest, which ended with violent clashes between police and protesters, was orchestrated by a Georgian politician.
Last week, Amnesty International classified Kosenko and two other Bolotnaya protesters, Artyom Savyolov and Vladimir Akimenkov, as "prisoners of conscience."
Kosenko insisted during the trial that police started the clashes on Bolotnaya.
Two participants in the Bolotnaya protest pleaded guilty previously and made a deal with investigators.
The trial of some 12 others is under way. More than a dozen more people are under investigation related to Bolotnaya.