In homicide cases, an Oklahoma criminal lawyer has several options for defense, including an "affirmative defense." In a murder case, an affirmative defense means the defendant admits to the killing, but is not guilty of a crime, either through self defense or an insanity defense.

Perhaps the most controversial of all defense strategies is the insanity defense. In making an insanity plea, the defense attempts to show that the defendant was insane at the time of the killing, and that he or she did not know right from wrong and did not understand the consequences of the actions.

The insanity defense is seldom used, and even more seldom used successfully. In Oklahoma City last week, however, a judge ruled that Dr. Stephen Wolf, who attacked and killed his 9-year-old son at the family home in Nichols Hills, was not guilty by reason of insanity.

Wolf's Oklahoma City defense attorney had his client evaluated by University of Oklahoma psychiatrist David H. Tiller, who found that Dr. Wolf was delusional at the time of his son's killing. Tiller reported that Wolf thought he was the devil, and therefore his son Tommy was the son of the devil.

According to the psychiatrist for the defense, Wolf believed at the time of the killing that "being the son of the devil is the worst evil there is and he had to release his son from that evil." On a recording of a 911 call made by Wolf's wife Mary, Wolf is heard saying, "Mary, he's the devil."

A police affidavit states that Wolf repeatedly told the officer who broke up the attack, "He's got the devil in him and you know it." Under Oklahoma law, the prosecution has the burden to prove a defendant is sane when the insanity defense is lodged. In Dr. Wolf's trial, however, the psychiatrist brought in by the prosecution concurred that Wolf was insane when he stabbed his son to death and attacked his wife when she tried to intervene.

Psychiatrists for both the defense and the prosecution noted Wolf's continued attempts to attack his son even after being restrained by police. They found that this persistence demonstrated his inability to understand that his actions were wrong. Oklahoma County District Judge Don Deason is sending Dr. Stephen Wolf to a state mental hospital. He cannot be released without the judge's approval, and may spend the rest of his life at the facility. The insanity defense is a complicated and controversial defense strategy.

State laws vary in regard to the rule that governs a determination of insanity, on whom the burden of proof is placed, and conviction versus acquittal options when the insanity defense is employed.

Recent insanity defense cases in Oklahoma include:

• Morgan E. Cline, 20, Mustang - convicted May 25, 2011 of shooting his father in bed in 2009. His Oklahoma violent crimes lawyer plans an appeal.
• Kassie Lakei Bills, 29, Oklahoma City - convicted in 2009 of the 2007 shooting death of a friend, Shequiea Thompson, 24. Her conviction was overturned on appeal in early May, and a new trial has been ordered.
• Eric Knox, 28, Oklahoma City - accused of killing his pregnant girlfriend in 2009. A judge granted a continuance in September 2010 to give his criminal defense attorney time to seek another psychiatric evaluation.

The insanity defense is only used in about 1% of homicide cases, and it is successful in only about 25% of those cases. Of the cases in which the insanity defense was successfully employed, 90% of the defendants had a previously diagnosed mental illness.