you get a very smart prosecuter to challenge the defendant as possibly 'unfit to stand trial' due to their illness. Bring along your (paid) psychologist who will 'determine' that Aspergers does indeed render the defendant as unfit, and then off to a psychiatric hospital to 'get better.' Apparantly, you only need one precedent to make this turn-the-tables scenario as citeable law.

Why would the prosecutor do that?

The prosecutor would do that because then they could put a "dangerous criminal" away for a very long time without having to bother with a jury trial. Or, on the flip side, so that they could get a sick individual the treatment they actually need, rather than incarceration that won't help them.

True. If the defendent is truly unable to understand why their crime was wrong, they cannot stand trial but the public must be protected from them, meaning they'll be locked up for a long time.

Yes, of course, the public must be protected from this dangerous individual who hacked into NASA's computers to find evidence of contact with aliens... How about the death penalty as some posters suggested?