A Vancouver police officer is expected to plead not guilty today to an alleged assault on a cyclist after a video of the incident was posted on Facebook.

The alleged incident happened in March 2013 in downtown Vancouver while Const. Ismail Bhabha was handcuffing cyclist Adishea Akhavan after pulling him over for riding without a helmet and running a red light.

When the cyclist asks the officer, "What is this for?" a video taken by Akhavan's friend, Mike Schwarz, appears to show Bhabha winding up and punching Akhavan in the head. At the time, Akhavan said the punch knocked a tooth through his lip.

The incident provoked outrage online when Schwarz posted the video of the incident on Facebook. Schwarz is expected to be the main witness at the trial.

Police had said the video captured only part of the incident and that Akhavan was "allegedly confrontational with police," and "escalated the situation."

West Vancouver Police conducted an independent investigation and recommended Bhabha be charged with assault in September.

The trial is expected to last three days.