I was reading about the two types on insanity pleas, known as 'NGRI' (Not Guilty by Reason of Insanity) and 'GBMI' (Guilty But Mentally Ill). For example, a good excerpt is here on Google Books.

However, something very obvious is bothering me:

How can you have a legal system where on one hand we consider insane people not guilty of their crimes and on the other say that they can be guilty? Isn't it a contradiction?

If insanity is a valid "excuse" to escape responsibility for a crime, then why isn't it always a valid excuse? Why would we allow insane people then to be found guilty? We already acknowledge in our legal system that insane people are not at fault.

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    Exactly which legal system are you talking about? The book seems to be about state law in the US, but that is effectively 50 separate legal systems. Is there really a single state that allows both pleas? Commented Aug 21, 2015 at 14:06
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    @NateEldredge: Exactly my question. I know that England and Wales went from "Guilty but insane" to "Not guilty by reason of insanity"/ Commented Aug 29, 2016 at 15:31
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    In English law you can be found guilty even though you are insane and, amongst other things, unable to stand trial. Also, if you (for example) insanely believe that the Devil has told you to kill someone, you are still guilty (because it would be a crime, even if what you believed were true) so not all forms of insanity will absolve you of guilt even if they existed at the time. Commented Dec 27, 2017 at 13:05
  • Typically, any given criminal court system has one or the other, not both.
    – ohwilleke
    Commented May 19, 2022 at 21:26

1 Answer 1


There is a clinical difference between insane and mentally ill.

An insane person is "so irrational in their behavior, or so unable to control it - so unlike 'us'" that they are not criminally liable (from earlier in the chapter).

Mental illness is "substantial disorder of thought or mood that substantially impairs judgement ..." (from near your link).

Clearly this is a subtle clinical distinction and will hinge on the expert evidence and the applicable law.

  • So you're saying that GBMI is less insane than NGRI? Commented Aug 21, 2015 at 14:40
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    Actually, I'm saying insane is not equal to mentally ill just like cancer is not equal to heart disease.
    – Dale M
    Commented Aug 21, 2015 at 21:30

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