It raises a privacy question: if you're naked, and nobody is around to see you, is it even a crime?

he's just an American with a disability.

I think your point is much more pointed than the usual unimaginative "mental illness" defense - if there's nobody to see, is it lewd?  The problem there is the issue of the security guards.

I mean, if I were the judge, I'd be asking, don't you have any more respect for me that to pitch an insanity defense here?  What, am I going to have to listen to PDs claim the prosecutor is insane for the next 10 years??  Come up with something imaginative, like "kidnapped by aliens", or "ghost virus in the computer".

I suppose I'd be inclined to tell the fellow to wear his fucking clothes and dismiss the case (under the doctrine of no harm, no foul) and let the prosecution appeal.

Jesus!  We have pedophiles, terrorists and Republicans in the country (OK, so they're redundant) and they can't come up with anything more important than WEARING CLOTHES AT MIDNIGHT??!!

They're probably taking it from the angle that even though there wasn't anyone around, there was the *possibility* of someone there to see him - janitor, security, another person working late.

The disability defense is a bit whack though.  A fine would be reasonable, as probably would a few sessions with a counselor.  If he repeats this behavior after this, then they should look into a good shrink for the guy.