Other ways to say 'I plead insanity'

I am writing a one act play about a trial. The evidence is piled against the defendant, and he wants to plead insanity. What are other ways of stating that? What are other ways to refer to that plea? I do not want to be overly repetitive by using only one phrase.

I was a prosecutor in the US, which does not mean I am right, but it might affect how you interpret my opinion.

First, "plea of insanity" is imprecise. In all US jurisdictions, when the defendant is required to enter a plea, the defendant may plead guilty or not guilty. Some jurisdictions allow a plea of no contest.

Insanity is an appendage to the above pleas. Most jurisdictions allow a defendant to enter a plea worded something like "not guilty by reason of insanity." A few jurisdictions allow a plea similar to "guilty but insane." The root issue of insanity in a criminal charge is the culpability of the defendant. If you believe it is necessary to not be "overly repetitive", then if you study the legal theories of culpability, then you will find much inspiration.

Nevertheless, legal terms such as "not guilty" and "insanity" are extremely precise, and when writing and speaking about law using synonyms for legal terms-of-art is highly problematic. I realize you are writing a play and not a legal memo, but consistently using terms of art will reduce ambiguity and confusion, so you may want to consider not using a synonym except when the speaker does not have legal training.

Off the top of my head, the only substitution that criminal lawyers might make is to say, "The defendant is claiming insanity." In that sentence, "claim" is a term-of-art that is an acceptable synonym for plea.

Good luck with your play. As a former trial lawyer, I don't envy your challenge of making a trial interesting to spectators!