TORONTO -- A Toronto police officer has been found guilty of assault causing bodily harm after breaking a cyclist's shoulder during a rough arrest.

Justice Susan Chapman found that Const. Douglas Holmes used excessive force when he shoved Oliver Santiago to the ground face first from behind after a traffic stop in downtown Toronto on Oct. 10, 2017.

"I find that PC Holmes was frustrated with Mr. Santiago for not immediately complying with his demands and that it was for this reason that he pushed him with considerable force from behind as he stood straddling his bike," Chapman wrote in her decision delivered last Friday.

Holmes and two other officers were working at the foot of Yonge Street by the water awaiting a protest around 5 p.m. that day. Holmes decided to act after seeing some cyclists ride through a red light.

He stopped Santiago who biked through the red light. Holmes asked Santiago three times for his identification, but the cyclist, who was now stopped straddling his bike beside the officer, was hesitant to do so and argumentative, court heard.

After Santiago paused on the final ask for identification, Holmes moved to arrest him while putting a handcuff on one wrist. The officer walked behind him and at that point Santiago, while straddling his bike, moved one of his arms. Santiago testified he was reaching for his wallet to get his identification.

Holmes then shoved Santiago from behind. The officer testified he pushed Santiago with both hands "to create distance between me and him" to give himself space to "re-evaluate the situation."

Santiago landed on the pavement face first, his helmet smashing off the interlocking brick. He broke his shoulder, his toe and sustained other injuries. Holmes finished handcuffing Santiago while the cyclist lay injured on the ground. Then the officer pulled out Santiago's wallet and wrote up the ticket. Santiago would later plead guilty to the offence and fined $325.

The entire incident lasted 66 seconds, the judge found.

Holmes testified he didn't ask Santiago if he was hurt because "a lot of people claim to be injured during an arrest." The two nearby officers dealt with Santiago, and Holmes later said he agreed that Santiago was hurt. Holmes didn't notify his supervisor or the provincial police watchdog -- the Special Investigations Unit -- because "there was no need to."

One of the other officers at the scene testified that he saw no issues with how Santiago was acting during the arrest. Two nearby workers testified they heard the crack of Santiago's helmet when it smashed the ground, calling it police brutality.

Holmes's defence argued that he was doing his job and following his training because Santiago was resisting arrest. The Crown argued Holmes used excessive force during a relatively minor infraction.

The judge noted she had "significant concerns" about Holmes's evidence.

"I found his evidence to be evasive and cavalier," Chapman wrote. She said Holmes made disparaging remarks about the other officers on scene and that he exaggerated both the seriousness of the offence and the danger of Santiago cycling through the T-intersection, which cars cannot travel straight through because Lake Ontario is on the other side.

"Though he was entitled to arrest Mr. Santiago, and even handcuff him, there was absolutely no need to push Mr. Santiago face down to the ground in these circumstances," Chapman wrote.