She’s leaning hard on the insanity defense.
Sure, he killed Polonius. Yes. But he’s crazy.
You see, he was in a lawless fit
In a brainish apprehension.
He was crazy.
(subtext: Please don’t prosecute my son. He’s mad. He’s insane. It’s not his fault.)
I mean – it’s a funny moment in this play.
Hamlet isn’t mad, as far as we know.
But this is an act for which we’d prefer him to be mad. We’d like to think a rational sane Hamlet would not murder an old man in cold blood. So – it becomes a question of whether we’d rather believe he’s crazy or murderous.
The Hamlet Project 