A more thorough explanation:

The ALI test, also known as the Model Penal Code test, is a legal standard used to determine if a person is criminally responsible for their actions. It is used in cases where the defendant claims insanity as a defense.

According to the ALI test, a person is not criminally responsible for their actions if they lack substantial capacity to either appreciate the criminality of their conduct or to conform their conduct to the law. This means that if a person has a mental disease or defect that prevents them from understanding the wrongfulness of their actions or from controlling their behavior, they may be found not guilty by reason of insanity.

For example, if a person with schizophrenia believes that they are being commanded by voices in their head to commit a crime, and they are unable to resist these commands due to their mental illness, they may be found not guilty by reason of insanity under the ALI test.

The ALI test combines elements of both the McNaghten rules and the irresistible-impulse test, which allows for consideration of both cognitive and volitional weaknesses. However, since the 1980s, many jurisdictions have narrowed the insanity defense and adopted a new test resembling the McNaghten rules, although portions of the substantial-capacity test continue to be used.