TULSA, Okla. (AP) - The second-degree manslaughter trial of a former Tulsa County volunteer sheriff's deputy is underway.

Robert Bates has pleaded not guilty in the April 2015 shooting death of Eric Harris during an undercover gun-sale sting.

Defense attorneys said during opening statements Wednesday that Bates made a "mistake" that was an "accident" that led to "excusable homicide."