Jurors have started deliberating in the second-degree manslaughter trial of a former Oklahoma volunteer sheriff's deputy who says he confused his handgun and stun gun when he fatally shot an unarmed suspect.

The jury received the case Wednesday after hearing nearly two hours of closing arguments in the case of 74-year-old Robert Bates.

The wealthy insurance executive fatally shot Eric Harris last year during an illegal gun sales sting.

Bates' attorneys have argued that Harris' drug use and cardiac health caused his death.

Bates faces up to four years in prison if convicted.

After the shooting, an internal 2009 memo surfaced that questioned Bates' qualifications. Bates also was a close friend of then-Sheriff Stanley Glanz and had donated thousands of dollars in cash, vehicles and equipment to the sheriff's office.