Take at least ten 8th grade level notes from this "(instrumental music) - Hey everybody, I'm <PRESIDIO_ANONYMIZED_PERSON>. - I'm <PRESIDIO_ANONYMIZED_PERSON>. [Together] - And today's question is - This is something that we hear all the time in TV and in film. Someone's lawyer says, oh well, they didn't do it because they're crazy. But usually, the explanation in the TV shows is a little bit more mysterious. We don't know exactly by what definition they are arriving at this. Or what means they're using to decide if somebody really is... - Hello! - Insane. And there's a difference here between insanity and mental illness. But how do the courts conclude this, and what are the problems with figuring out if somebody is legally insane? - Why would being mentally ill excuse someone from criminal guilt? How is a jury of non-experts or non-mentally ill people qualified to figure if somebody is mentally ill? And then third, what sort of mental illness, what degree of mental illness constitutes actual insanity? And then fourth, and probably the most difficult, is how can we prove that someone is or was insane? It's tricky, you know? - Yeah, those are great concerns. And as we said, there's a difference here between mental illness and insanity. Mental illness is a legit psychiatric disorder, whereas insanity is sort of a cultural concept. In a US court of law, mental illness and insanity may be related, but they are by no means synonymous. And this applies in courts in some other countries as well. Mental illness at the time a crime is committed is a prerequisite of not guilty by reason of legal insanity, but legal insanity itself is a little bit different. Somebody has to meet three conditions before they are found to be legally insane. - Right, yes. One, if they have a mental illness such that they did not know what they were doing was illegal. Or, two, if the mental illness was such that he or she just did not know what they were doing at all. And then three, and this one's a little bit frightening, he or she felt like they were compelled to do this by an irresistible force. - So then, why is a person who actually committed these crimes somehow not guilty of them? Well it all goes back to when the fundamental tenets of the US justice system, which is intent. You have to intentionally commit a crime to be found guilty of it. So, for example, if you accidentally bump into someone and they fall on the ground and injure themselves, it's going to be looked at differently than it would if you walked up to a person, stepped on their foot, pushed them, or punched them, you know, if you intentionally meant to hurt them. And the idea of a mental illness, skewing the perception of reality such that a person doesn't actually understand the reality of what they're doing, is central to the idea of this defense. The intent to commit the crime is not there. - Right, so to bring it all back around, to prove legal insanity, the defense team has to do two things. First, they have to have expert testimony proving the defendant is mentally ill. Second, they have to also explain how this mental illness removed the defendant's ability to reason, to understand what they were doing, or to do it intentionally. So the jury is not actually deciding whether the defendant is insane or mentally ill, what they are deciding instead, is whether the expert testimony has proven this mental illness or insanity, and whether or not that means that the defendant really did not intentionally commit the crime. This means that mental illness, by itself, is not really a legal defense. If someone is mentally ill, and they intended to commit a crime, or that they jury rules that they still intentionally did this illegal act, then they're still going to be guilty. - So that's it. That's how not guilty by reason of legal insanity works, when it does. [Together] - Thanks so much for watching. - If you have any other questions, we'd love to hear them in the comments. If you'd like to check out some videos, we've got these here as well. Go ahead and click Like or Subscribe, and we will see you next time. Good work, I think that went well. (electronic music)"