Everyone can plead insanity, that's what is so insane about our legal system. You could always use the "but I was binge drinking" excuse that seems to work in Fayette County. You can get away with anything when you use that excuse.

There is some difference between being drunk with whiskey or beer, and being insane for another reason. Drinking is voluntary, except for severely addicted alcoholics, and even that is a choice.
I am not talking about whether insanity should moderate the guilt of someone accused of a crime, but just how it is more favorably determined for some of us than for others.
If it can be assumed that if someone is absolutely unaware or overwhelmed by insanity, temporary or otherwise, then maybe that can be treated and the future danger from such a person removed. Payment for the crime is a jury function, but the charges often are the determining factor, not the verdict.
I sometimes have a question when a mother for instance, who might kill her children deliberately, sane or insane, is quite often considered to have extenuating circumstances due to being a woman. An ignorant, or maybe also insane man might be the cause, they think!
Well, it seems to me, with the exception of Ol Helter Skelter, himself, almost all insane people who kill seem to be ok as soon as the trial is over, or at least appear to be---not wanting to kill anyone else.
Status in the community, wealth, type of lawyers, appearance, intelligence, and most of all, whether the citizens, in general have fear of you, which shouldn't make much difference as to guilt.
That is why many go to jail for ten years for grabbing a loaf of bread and running away, and others clean out your bank account and get probation.