31: Why Almost Everyone Gets the Insanity Defense Wrong | Case Notes

31: Why Almost Everyone Gets the Insanity Defense Wrong | Case Notes

July 12, 2026 · 22 min · Episode 31

About this episode

This episode explores the complexities and misconceptions surrounding the insanity defense in criminal law through a conversation with forensic psychologist Dr. Joni Johnston.

Why do so many people misunderstand the insanity defense? It's one of the most debated concepts in criminal law, yet also one of the least understood. Popular culture has created the impression that defendants routinely "get off" by pleading insanity. The reality is far more complicated. Legal insanity is not the same as mental illness, psychopathy, or a psychiatric diagnosis, and successful insanity defences are exceptionally rare. In this episode of UNMARKED: Case Notes, I speak with forensic psychologist Dr. Joni Johnston about what the insanity defense actually is, how courts determine criminal responsibility, and why so much public discussion gets it wrong. We examine the legal standards behind the defense, common misconceptions, and the role mental illness can—and cannot—play in determining guilt. If you've ever wondered what "not guilty by reason of insanity" really means, this conversation offers an evidence-based look at one of the most misunderstood issues in the criminal justice system.

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