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Understanding the Insanity Defense in California

Criminal defendants who plead not guilty by reason of insanity in California must meet the criteria of the M’Naghten test. Under this standard, they must be able to prove that they didn’t understand the nature and quality of the crime or they didn’t understand the difference between right and wrong at the time the crime was committed. To succeed, an insanity defense must be proven by a preponderance of the evidence, which means the court must find that it is more likely than not that the defendant was legally insane at the time he committed the crime. Typically, a defendant will need expert testimony in order to meet the preponderance standard.

The M’Naghten test derives from an 1843 English case in which Daniel M’Naghten killed Edward Drummond, whom he wrongly believed to be Prime Minister Robert Pell. (M’Naghten thought the prime minister was leading a conspiracy against him.) It was determined that M’Naghten was suffering from “morbid delusions” at the time he killed Drummond and was therefore not able to distinguish right from wrong. He was found not guilty on that basis. The insanity defense in California has followed the M’Naghten test since the 19th century, with some slight variations over time.

A common misconception held by defendants is that an acquittal by reason of insanity is the same as other not-guilty verdicts. Being acquitted by reason of insanity does not mean that the defendant is free to resume his life. He is relieved of criminal responsibility but will be committed to a state psychiatric hospital for treatment in lieu of criminal punishment. If you are acquitted of a crime by pleading insanity, you can expect to remain committed until one of these conditions is met:

  • The medical professionals providing your care decide that you are no longer insane.
  • The time equivalent to the maximum prison sentence for your crimes has passed.
  • You’re approved for an outpatient program.

As decided in People v. Robinson, an insanity defense cannot be claimed by defendants whose sole argument is that they are alcoholics or drug addicts, although a legal defense of involuntary or voluntary intoxication may be available.

If you wish to claim insanity as a defense to criminal charges in California, an experienced criminal defense attorney who understands state law can help you understand your options. Amber Gordon, Attorney at Law represents defendants in Hollywood and throughout the greater Los Angeles metro area facing a wide range of charges. Call us at 310-773-3980 or contact us online to arrange a consultation at our Los Angeles office.

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