Legal Definitions - McNaghten Rule

The McNaghten Rule is a legal test used to determine criminal insanity in a defendant during a criminal trial. According to this rule, a defendant is considered legally insane only if, at the time of the crime:

1. They did not know what they were physically doing, or
2. They did not know that what they were doing was wrong.

For example, if a person with a delusional disorder believed that their violent actions were in response to the will of God, they would not be held criminally responsible for their actions under the McNaghten Rule.

Another example could be a person with severe dementia who accidentally sets fire to their home. They may not have known what they were doing or that it was wrong, and therefore would not be held criminally responsible.

The McNaghten Rule is one of the earliest and most commonly used tests for criminal insanity. It is used to determine whether a defendant had the mental capacity to understand the nature and consequences of their actions at the time of the crime.