The trial of a former volunteer deputy in Oklahoma who was charged with manslaughter will have its closing arguments and jury deliberations beginning Wednesday.  The defendant has pleaded not guilty over the said charge.

Robert Bates, who was charged to a second-degree manslaughter following the death of Eric Harris in April 2015, has entered a not guilty plea, according to Salon. Both sides began to wrap up their cases on Tuesday's trial, giving the witnesses a rebuttal over the victim's death.

During the trial, a doctor specializing in trauma, Dr. Mark Brandenburg, testified for Bates' defense. He told that the victim died because he suffered from a heart attack, instead from the loss of blood or a collapsed lung after the gunshot. Dr. Brandenburg also insisted that the medical examiner's claim that Harris "bled to death" is not true.

A cardiologist also gave a testimony for the defense. Dr. James Higgins testified that the cause of death of the victim was not from the bullet, ABC News reported. Higgins explained, "It didn't hit the conduction system of Harris' heart so it had no effect on its electrical function."

However, an emergency room doctor, Dr. Gajal Kumar, gave her testimony against Bates, insisting that the medical examiner's opinion is corect. She added that she performed a medical procedure on the victim when he was rushed to St. John Medical Center, "But at that point he'd lost too much blood to do anything about it."

If convicted, the 73-year-old defendant faces up to four years in jail, Courthouse News cited.

The incident involved Bates who shot Harris, 44 years old, during a gun sale sting last year. According to Bates, he mistakenly shot Harris, thinking he was holding a Taser.

He also said he would not testify. The jury is set to return Wednesday morning and hear closing arguments before beginning deliberations