I'd think being a Sociopath a form of insanity. It means something just isn't working inside that brain of his that would ordinarily prevent him from doing heinous things.
You're wrong. I'm not debating whether the Joker is "crazy," because that's a subjective term, but sociopathy is NOT a form of insanity by medical or legal definition. It's a mental disorder, like depression et al., but it does not qualify. To my knowledge, no one in the United States has ever been acquitted with an antisocial personality disorder defense, BECAUSE it doesn't qualify as insanity by any reliable definition. Whether the Joker is "crazy" or "nuts" is a broader topic, but sociopaths aren't considered insane by the law or medicine that defi ne them.
A lot of people here are parroting what the psychologist said on the history channel's pyschology of the Dark Knight. He only explained one test, the irresistible impulse test for insanity. But there are 4 legal insanity tests which vary depending on the jurisdiction. Joker being subject to the M'Naghten test for insanity might have an interesting outcome contrary to the irresistible impulse test . The M'Naghten test was used in the Andrea Yates trial which resulted in her being found not guilty b/c of insanity. This was the case of the woman who drowned her children b/c she believed Satan was inside her and she was trying to save them from hell.
I haven't seen that program, so I'm not sure if you're saying they considered him "insane" or "sane" by the irresistible impulse test. I will say, though, that this test is almost NEVER used. I'm not sure why it would be brought up at all. Even then, I think it's even less convincing to apply that test to him, because he picks and chooses when he kills someone and when he doesn't. He's very much in control of his actions for most of the film. Someone who failed the irresistible impulse test wouldn't be able to function in the calm, calculated manner he does. They would be severely and visibly disturbed by the inability to resist their urges. They couldn't calmly sit down at a table and convey a plan, plan an elaborate bank heist, coordinate Harvey and Rachel's predicaments, organize the reverse-hostage crisis at the end with the clowns and doctors. He is much, much too rational for an individual who would qualify for that test.
As far as the M'Naghten rules go, again, I'm not sure which insanity test you're saying might deem him possibly insane, but there isn't much here either. You reference Andrea Yates, but she had a history of wild, psychotic, delirious, and delusional episodes prior to the deaths of her children. She was on Haldol, a very powerful anti-psychotic usually meant for schizophrenics, and killed them after the prescription was discontinued. As far as the actual deaths go, she was suffering from command hallucinations (in the form of the voice of Satan) at the time. The Joker isn't, to our knowledge, reacting to internal stimuli, or acting in a manner where he's lost complete control of his mind or body. He has a twisted view of the world and may think of himself and Batman as on another level than the rest of society, but he isn't suffering from an overt psychosis that would render him insane by the standard of the M'Naghten Rules, the way that Andrea Yates was.
Disease of the mind - Doesn't apply, the Joker doesn't have a physical disease (i.e. epilepsy) that alters his brain and forces him to commit crimes. Chemical imbalances like depression don't qualify under this rule.
Nature and quality - I went through this up above, but he knows that he's stabbing people and that they're going to die. Therefore, this rule doesn't apply.
Right and wrong - The Joker knows it's against the law (and conventional moral standards) to kill people. He does it anyway. He likes violating it. Again, this is a matter of understanding that your actions are against the law. Simply deciding not to believe in the law or reject conventional morals isn't enough, or every criminal would be "insane." This rule doesn't apply.
Specific intent - Doesn't apply, refers to committing an act (i.e. setting off a bomb) without the "intent" to commit another (i.e. murder, because someone died in the explosion). He knows people will die.
I would argue (based I will admit, on my favorite Joker stories. I'm well aware that other interpretations are just as valid) that it isn't simply that he doesn't care, but that the reality of his actions doesn't register to him as real. He understands the consequences of his actions, but in the way you or I understand a work of fiction. It may be "real" to him in the sense that it has meaning to him, but it doesn't register to him that the things he does matter. Not out of apathy, but because the way he perceives reality is fundamentally different from ours and very much detached from reality.
It's an interesting discussion! I hope I'm not coming off as adversarial at any point here. I understand where you're coming from; IIRC, the Joker has suggested that he and Batman are on another level of reality than everyone else. It's an interesting hypothesis. I think it applies more to the comics than the film, IMHO, because I strongly get the feeling that it's more of a "game" to him in TDK than it is "make-believe." What you're suggesting - that he's not able to recognize that his acts are real - could muddy the waters and give rise to questions about how crazy he is from a non-medical/legal standpoint. It's ultimately still not legal insanity at this point in time, however, because the current insanity "tests" don't have any criteria that would include that defense. The closest thing I can think of to what you're suggesting is depersonalization/derealization, which quite a few criminals have exhibited to some extent, but not received an not-guilty-by-reason-of-insanity verdict for before. A lot of the Nazis claimed that they lost touch with a sense of self and had a distorted sense of reality, which is probably true to an extent, but that in itself hasn't been medically or legally held to constitute insanity. At this point in time, where the law is concerned, if you don't have a physical brain disorder, know that your actions will cause a death/rape/whatever, and know that it's legally a crime, you are legally sane, even if you claim it took place in an alternate/fictional reality.
Like the above poster has said the Joker has no since of reality, in a way he is terrorist. He knows the crimes and the actions he commit will harm or possibly kill people but he continues and doesn't care about the consequences . Than you have to take into account he doesn't care about his own life, he doesn't fear anything not even death. He may not be legally insane to some psychologist, but to me he seems to be.
I'm not arguing whether he's "crazy." The measure of "crazy" is subjective. The original question is "is he legally insane?" The answer is no, because this is defined very precisely. You're saying "He knows the crimes and actions he commits will harm or possibly kill people," and then adding a "but." There is no legal but. That is the legal definition of sanity - the ability to distinguish right from wrong and know what you're doing at the time that you're doing it. "Not caring" or "not fearing" does not constitute insanity. If it did, almost every serial killer in existence would be legally insane. You mention terrorists, which is a good analogy, but Osama Bin Laden, Al Qaeda, et al, have NO chance of ever being deemed legally insane because they know exactly what they were doing. I think a lot of the people saying "he kills people and doesn't care" are confusing "legal insanity," which has a clear legal definition, and "he's insane, man," which is basically "crazy," an extremely subjective concept.
