March 2013 Bar Bulletin
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March 2013 Bar Bulletin

Mental Disease or Defect Defenses: Insanity or Diminished Capacity?

By Christina Schuck


Recently, Christopher Monfort, the man accused of fatally shooting Officer Tim Brenton and wounding Officer Trainee Britt Sweeney while they were parked in their patrol car on October 31, 2009, notified the court he intends to plead not guilty by reason of insanity. Monfort is charged with aggravated murder and attempted first-degree murder and claims that due to a mental disease or defect he was unable to determine right from wrong at the time of the shooting.1

In addition to the insanity defense, a defendant suffering from a mental disease or defect could also employ the diminished capacity defense. While the two defenses are related, they are conceptually and procedurally different.

The insanity defense functions as an "excuse." When pleading insanity, the defendant contends that although he has harmed society, because of his mental disease, he should not be blamed or punished for causing that harm.2 In recognizing an insanity defense, society has determined an insane defendant is not morally blameworthy.3

Under Washington law, insanity is an affirmative defense. Thus, the prosecution is not required to prove the defendant is sane; rather, the defendant bears the burden of proving he is insane. Washington follows what is called the M'Naghten Rule, which stems from an 1843 English case and is codified in RCW 9A.12.010.4

A successful insanity defense requires a defendant to prove by a preponderance of the evidence that he was insane at the time of the commission of a charged crime.5 To do so, the defendant must establish that at the time of the charged crime, as a result of mental disease or defect: (1) he was unable to perceive the nature and quality of the act of which he is charged; or (2) he was unable to tell right from wrong with reference to the particular act charged.6

Under RCW 10.77.030, evidence of insanity is only admissible if the defendant files written notice of his intent to plead insanity. He must do so at the time of the arraignment, within 10 days thereafter, or at a later time if the court permits for good cause.7 Interestingly, although Monfort was arraigned on December 14, 2009,8 he did not notify the court of his intent to plead insanity until February 1. After the court receives this notice, on its own or by motion of either party, it can appoint or request the designation of a qualified expert to evaluate and report upon the defendant's mental condition.9

If the issue of insanity ends up before a jury, the jury first considers whether the defendant committed the act charged.10 If the answer is yes, the jury employs the M'Naghten Rule to determine if the defendant is acquitted because of insanity.11

An acquittal is not the end of the inquiry, however. If the jury also determines the defendant is a substantial danger to other persons and presents a substantial likelihood of committing criminal acts jeopardizing public safety or security, the court must then order hospitalization or a less restrictive alternative treatment.12

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