The defense completed presenting its case Tuesday in the second-degree manslaughter trial of a former Oklahoma volunteer deputy charged with killing an unarmed man after presenting testimony that the gunshot did not kill the man.

Attorneys for Robert Bates finished Tuesday after presenting a doctor who said Eric Harris died of a heart attack, not blood loss and a collapsed lung, as listed in an autopsy report.

Trauma Dr. Mark Brandenburg testified for the defense that Harris' heart attack was caused by elevated adrenaline and a high level of methamphetamine in his system when he was shot.

Brandenburg said the medical examiner's opinion that Harris Bled to death is "absolutely untrue" and that there was no evidence of a collapsed lung.

Brandenburg acknowledged he was not involved in the treatment of Harris, but said he has reviewed medical records in preparation for his testimony for the defense.

Cardiologist James Higgins also testified the gunshot did not cause Harris' death, saying the bullet didn't hit the conduction system of Harris' heart so it had no effect on its electrical function.

Bates, who has pleaded not guilty and said he mistook his gun for his stun gun when he shot Harris, said in court he would not testify and, in response to a question from Judge William Musseman, said he is satisfied with his attorneys.

"Absolutely, I'm tickled to death," Bates said.

Prosecutors plan to call a cardiologist and emergency room doctor as rebuttal witnesses. Closing arguments will follow the rebuttal witnesses and Musseman has said the trial may go to the jury as early as Wednesday.