What is required for a judge to acquit someone found to have no mens rea due to mental illness?

A judge can acquit a defendant found to have no mens rea due to mental illness if the defendant is established to be insane at the time of the offense. This principle arises from the understanding that accountability in criminal law is closely tied to a person's mental state during the commission of a crime. If a defendant is judged to be insane, it indicates they lacked the capacity to understand the nature of their actions or the distinction between right and wrong, which removes the requisite mens rea necessary for a conviction.

The other options do not align with the legal standards for determining responsibility in criminal cases. A confession is not required for an acquittal; rather, it's the mental state that matters. Additionally, the standard of evidence being "overwhelmingly positive" misrepresents the burden of proof, which must be met in criminal trials. A guilty plea contradicts the premise of acquittal, as a plea of guilty would entail a criminal conviction. Hence, being found insane is central to the legal determination that leads to acquittal in these circumstances.