Mustang man claims insanity in slaying (newsok.com)
Murder defendant, Morgan E. Cline, of Mustang, claims he was insane when he fatally
shot his father in bed in an Oklahoma City home. Insanity defense is used rarely at trials.


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Defense attorney Marna Franklin told jurors Tuesday in her opening statement that Cline was “a very, very sick boy” who did not know right from wrong when he shot Richard A. Cline, 58, in bed at the oilman's Oklahoma City home early April 18, 2009.

She said the high school dropout believed people could read his thoughts, experienced hallucinations of things crawling on his skin and heard voices in his head that he thought were demons or ghosts.

“Morgan Cline is not your normal kid. He is mentally ill,” the defense attorney said.
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more at newsok link above
A study of the various types of defense strategies used in eight states found that the insanity defense was employed in less than one percent of all criminal cases, and that when it was used, the insanity defense was successful in only about 26 percent of the cases. Moreover, of the cases in which the insanity defense was successful, 90 percent of the defendants had already been diagnosed as mentally ill.
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http://www.criminal-law-lawyer-sourc...y-defense.html
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Henry Cline, 16, testified Wednesday he saw his brother from a distance outside their father's house when his brother turned himself in. “Morgan looked completely not like himself. Out of body, I guess,” Henry Cline told jurors.

Henry Cline said, “What I meant by that – this may sound weird – but, like, he didn't have a soul.”
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more at newsok link above
The insanity plea was not a sudden idea on the part of the defense; this article's from April 2009:
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His attorney said that he may use an insanity defense at trial.

"He’s a real troubled kid,” said the suspect’s attorney, John Coyle.
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http://newsok.com/oklahoma-city-susp...adlines_widget
While insanity defenses are so rarely used as to be not worth the rage that we feel when someone does in effect try to excuse his or her behaviors with that plea, I'm a bit dubious about it in this case. (Googling will produce a number of case specific articles.)