Need your help !!!

[Phá Long]

hi guys,

I have an assignment: Design and create a montage or collage for a short story.

And i have picked (random) this: "Guilty beyond all doubt. Plead insanity."

The problem is, i dont know what it is !!! i google it and just know that is a kind of 6-word-story ... i i dont understand correctly what it means.

Please anyone could explain to me what these story talking about ?

Thank you.