COLUMBIA, Mo. -

Former Columbia police officer Robert Sanders went on trial Thursday for assault charges filed in 2012.

Sanders is accused of shoving and injuring an inmate in a CPD holding cell. The probable cause statement says there was a brief exchange of words between Sanders and the inmate.

A department video camera shows Officer Sanders shoving the man backward, causing him to hit the back of his head against the wall.

Sanders was then fired from the department in 2011.

Baker said when officers arrested him, he was pepper-sprayed. He said he did not remember much after that, because he could not see and there was not any water in his holding cell. Baker explained when he asked, officers said he could use the toilet water. He then went into a rant and started kicking the door.

Sanders lawyers argued throughout the day Sanders asked him to calm down and sit. But Baker did not remember that.

Other officers in the area at the time confirmed Sanders asked him the question, and they were afraid Baker was going to hurt himself. They said protocol is to put suspects in handcuffs to keep them from harming themselves.

Sander's lawyer said Baker fought with officers several times and should have been considered dangerous. He explains Sanders went in and did what was necessary to get Baker on the ground and in handcuffs. But Baker said it was completely unnecessary.

The internal affairs commander testified, saying they found Sanders did not violate procedures or polices in regards to the use of force.

Sanders has a bench trial, meaning it is a trial by judge and not a jury.