A more thorough explanation:

Definition: This phrase refers to a legal term used to describe a person who is so mentally ill that they cannot be held responsible for their actions. It is similar to the term "guilty but mentally ill."

Example: If someone commits a crime but is found to be "but so insane as not to be responsible," they may be sent to a mental health facility instead of prison.

Explanation: This legal term is used to determine whether a person is mentally capable of understanding the consequences of their actions. If they are found to be "but so insane as not to be responsible," it means that they cannot be held accountable for their actions because they were not in the right state of mind. This is often used in criminal cases where the defendant has a history of mental illness or has exhibited signs of mental illness at the time of the crime.