Also known as:product-of-mental-illness test · product test · Durham rule · product test for insanity
Written by attorneys · grounded in primary & secondary sources — see below
A test for criminal insanity that requires acquittal when the charged offense resulted from a mental disease or defect. The offense qualifies as the product of the condition if the defendant would not have committed the crime but for the mental disease or defect.
Sources & Authorities
How it applies
Common Examples
2
Ransomware Attack by Delusional Engineer
Jordan, a senior engineer at ByteForge, secretly disabled network security at Valley General Hospital and deployed ransomware. For months he had suffered psychotic delusions that the hospital servers transmitted mind-control signals targeting him. Two psychiatrists testified that Jordan suffered from a serious mental disease and that but for this disorder he would not have carried out the cyberattack. In a jurisdiction applying the product test the jury must acquit Jordan by reason of insanity.
Assault by Nurse with Postpartum Psychosis
Carla, an emergency room nurse at Riverside Hospital, suddenly attacked pharmaceutical representative Dana with trauma shears. Defense experts testified that Carla suffered from severe postpartum psychosis and that but for this psychosis she would not have attacked. In a jurisdiction applying the product test the jury must acquit Carla by reason of insanity if it credits the experts.
Select any source to read its text and confirm it supports the definition.
Common Law
Casebooks
Clark v. Arizona548 U.S. 735, 752 n.20, 126 S.Ct. 2709, 165 L.Ed.2d 842 (2006)
Common questions
Frequently Asked
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What is the key inquiry under the product test for insanity?+
The jury asks whether the charged offense was the product of a mental disease or defect. This means the defendant would not have committed the crime but for the mental condition.
Supporting sources
Does the product test require proof that the defendant could not distinguish right from wrong?+
No. The product test focuses solely on causation. Acquittal follows if the offense resulted from the mental disease even if the defendant understood the act was wrong.
Supporting sources
How does the product test differ from the irresistible impulse test?+
The product test examines whether the offense was caused by the mental disease. The irresistible impulse test instead examines whether the defendant could control conduct or conform to the law.
Supporting sources
What evidence supports a product-test acquittal in an essay setting?+
Expert testimony that the defendant would not have committed the offense but for the mental disease, together with immediate post-incident statements linking the act to delusions, supports acquittal under the but-for standard.
Supporting sources
548 U.S. 735, 126 S. Ct. 2709, 165 L. Ed. 2d 842 (2006)Criminal Law
…of American standards. The main variants are the cognitive incapacity, the moral incapacity, the volitional incapacity, and the product-of-mental-illness tests.[^maj-7] The first two emanate from the alternatives stated in the M’Naghten rule. The volitional incapacity or irresistible-impulse test, which surfaced over two centuries ago (first in…