A plain clothes police officer in Idaho who was caught on camera forcefully smashing an elbow into a man's head, despite the fact that he was already restrained, has been charged with assault.

Pocatello Police Detective Steven Westfall was captured on dashcam, forcefully pressing his forearm into James Rutherford's head, while two other officers already had him restrained and face down on the hood of a car.

Westfall is then seen raising his arm as high as he can get it and bringing down his elbow into Rutherford's head, and holding it there with as much force as he can muster.

The arrest occurred when police were called to an IRS building with the caller suggesting Rutherford had a knife and was arguing with a security guard, while refusing to be searched.

In reality, Rutherford did not have a knife. However, he was armed with something the cops thought was much more dangerous – a cell phone. Rutherford attempted to film the cops, but he was seized by the officers, cuffed, and led out of the building.