He displays malice and forethought, the fact that he goes into detailed strategy and planing to kill means by law he is completely responsible for his actions and could be legally executed so really it is the fault of Gotham City that he keeps getting sent to Arkham and escaping because legally they can put him on death row   

*Denny Crane!*

I dont think there is a death row in Gotham.

He is clearly insane though, maybe not in that he can still plan such horrific acts, but just in the fact that he can conceive of them.   

I remember the issue when Joker killed the doctor when he couldn't prove to him that he is insane.

Jason made a comment about that once,

no he's still legally insane, every doctor in Arkham (Gotham's official medical advisers on the subject) agrees that he's not responsible for his actions because he knows what he's doing is wrong but he doesn't understand what wrong is. To him (at least from the doctor's perspective) Joker doesn't understand what the difference is between giving someone a box of chocolates and cutting off their fingers. Now you can argue whether or not this is true based on what we the readers know about him, but this is a question of what the doctors and judges/jurys think about him...but all this is really moot Joker: Devil's Advocate proves that they could find him guilty because he isn't insane but they need him to do the right kind of crime in order to convict...

It is well established that Joker is crazy and that his mind is one of a kind. Martian Manhunter could only enter it for a short time before he started going insane. He was able to give Joker momentary sanity by "correcting his mind" telepathically. He could not hold this for long but while sane the Joker was disgusted in himself and his actions and wanted punishment and was scared to be turned back.  So no he is not sane 

He's certainly insane,this was proven in the Demon Laughs storyline where he takes a dip in the Lazarus pit,hell going sane kinda proves that as well.

"Legal" definitions always make me laugh, until I realize that they're being used to decide people's fates, and then I get depressed and have to go lie down for awhile.

I can only speak for the law in my home state when I say this.  There is no longer "not guilty by reason of insanity".  You can be found incompetent to stand trail in which case you go to some hospital or psych ward or institute for treatment.  When the Doc's decide you are sane enough you re-stand trial where the judge decides if punishment is merited.  If the Joker were to stand trial in my state he would be found unfit to stand trial and go to a Maximum Securtiy Psych Hospital for treatment until he was fit to stand trial.  When he would be fit to stand trial the judge would then decide, with a Doctor's report of illness, side-effects of illness, and treatment needed, weither or not he was responsiable for his actions.  If found resposiable he goes to jail, life in prision, death row or whatever.  If he was found not responsiable and no futher danger to socity he goes free under a Doctor's care until the Doctor and the Judges decide he's fine and free to enter socity. 

*Denny Crane!*

I figured this out over a year ago, so I was rather pleased when at least 3 comics mentioned it this year. 
 
But you know, if Joker feels any love for Harley at all, it means he's also faking his Sociopathy. 
 
All I know is that he's clearly the best actor in Gotham.

@entropy_aegis: @son_of_magnus: @sydpart2:

I know this thread has been dead for almost 2 year but I found this interesting.

2. (Law) Law a defect of reason as a result of mental illness, such that a defendant does not know what he or she is doing or that it is wrong

http://www.thefreedictionary.com/Insanity

IIRC, Joker has called himself many many times "The Clown Prince of Crime" implying that he knows the things he does is criminal.

@deviousbastard: That's the common, pop culture quick definition. A lot of books and movies misrepresent the legal insanity defense that way. It's a simple definition and it can be used as a short cut plot contrivance. This misrepresentation isn't doing the general public any favors. It just confuses things. Being able to function and make elaborate plans and act them out does not make a person sane.

The truth is, its more complex than that. A big part of it is compulsion. Even if the subject knows right from wrong does he have the option of choosing right and not doing the wrong? Or does his insanity control him and remove the ability to control himself.He knows its wrong but he just can't stop.

Joker fits this to the letter. In part 4 of Death in the Family Batman even yells at him "Joker you have to stop" and Joker starts yelling louder and louder "I can't I Can't I CAN"T" even as they fight. The Specter, Martian Manhunter, Raven, and The Archangel Zauriel all journeyed into Joker's mind and soul and proved Joker has no choice, no control, and no conscious. Batman described Joker as having a sort of "unholy innocence."

I almost forgot the psychological aspect, the physical construction of the brain is also a major factor and can be used in court. The neurologist states how abnormal and damaged Joker's brain is. He states it quiet definitively. "This guy never had a chance at sanity." It's not even debatable.You can't "act" brain damage or abnormal development.

I'll have to scan the page from Secret Files, The Joker's Last Laugh and load it into my images files. This question keeps getting brought up again and again when its been definitively answered over and over as canon.

YES THE JOKER IS INSANE. To the point that it counts as his super power in a way. The occasional writer trying to be clever by saying other wise is irrelevant. For 73 years of he has been insane. As the man himself puts it "Gloriously so!"

It's comics not real life

I bet in the dc universe there is an amendment about meta humans on the constitution

@thejokerha: OIC, that chemical bath screwed his brain up. Seems pretty pointless to put him in a psychiatric hospital when there is no chance at him being sane again.

@deviousbastard: ok, so he knows that his actions will be considered criminal... but that doesn't mean that he thinks his actions are "wrong". He could see them as unjust laws and that his actions are right.

This is an interesting question. The answer points to how the legal system sees insanity. Do you think the legal definition covers all it's bases? do you think it does enough? Who is it there to protect?

This thread just blew my mind.