Also known as: uncontrollable impulses · irresistible impulse
Written by attorneys · grounded in primary & secondary sources — see below
A volitional defect arising from mental illness that renders a defendant unable to control his actions or conform his conduct to the law even when he understands the wrongfulness of the act. The defect may develop gradually or exist over an extended period rather than arising in a sudden outburst.
Uri Underwood, a benefits clerk with severe depression and psychotic episodes, believed his supervisor persecuted him. Over several months an inner pressure to smash the supervisor's computers built beyond his ability to resist. He entered the closed office on a weekend and destroyed the equipment. Under the irresistible impulse test the jury credits expert testimony that mental illness destroyed his capacity for self-control and acquits him.
Uliana Ustinova, diagnosed with a long-standing sexual disorder, repeatedly molested children when stressed and testified she could not control the urge. The state seeks civil commitment after her prison term. The court finds the documented inability to control impulses satisfies the statutory dangerousness requirement and orders continued confinement.
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Unity Underhill was acquitted by reason of insanity after an assault she could not resist due to mental illness. Years later she seeks release. The state must prove she remains dangerous because of an ongoing inability to control her conduct rather than mere mental illness alone.
Ulric Unger, a public figure, sues a publisher for a false story. The court requires proof of actual malice. Evidence that the reporter felt an overwhelming internal pressure to publish without verification does not excuse the failure to investigate and does not defeat the constitutional standard.
Ursula Upton burns a cross on a Black family's lawn. The city defends its bias-motivated crime ordinance by arguing the conduct reflects an uncontrollable impulse rooted in prejudice. The court strikes the ordinance because content-based restrictions on speech cannot be justified by claims of irresistible impulse.
Ursula Ung, charged with murder, claims an uncontrollable impulse from mental illness. The state requires her to prove the defense beyond a reasonable doubt. The jury instruction on that burden is upheld because the Constitution permits the state to allocate the risk of non-persuasion on the volitional element.
No. The traditional irresistible impulse test expressly permits the inability to control conduct to develop gradually or exist over time. A defendant who experiences steadily mounting pressure rooted in mental illness can still satisfy the test even if the conduct was planned over weeks or months.
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No. The test is volitional rather than cognitive. A defendant who understands the wrongfulness of the conduct may still be acquitted if mental illness destroyed the capacity to conform behavior to the law.
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The irresistible impulse test focuses on whether mental illness prevented the defendant from controlling actions. M'Naghten requires a defect in reasoning that caused inability to know the nature or wrongfulness of the act. Loss of control alone does not satisfy M'Naghten.
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…statute amounts to no more than a legislative adoption of the “right and wrong” test of legal insanity in preference to the “irresistible impulse” test.[^maj-15] Knowledge of right and wrong is the exclusive test of criminal responsibility in a majority of American jurisdictions.[^maj-16] The science of psychiatry has made tremendous…