Dubious Notions

Eugene Volokh of the Volokh Conspiracy recently published this post. He quotes the language of some Indiana and Tennessee law defining the crime of public nudity. Volokh calls particular attention to this clause:

"the showing of covered male genitals in a discernibly turgid state."

I'm particularly gratified to note the precise exposition of this important bit of legislation. However, several questions arise:

• What degree of scrutiny would be required to define the requisite "discernibly turgid state"? Would a casual glance be the standard or would the effort required for deliberate, concentrated examination be acceptable?
• Shouldn't there be some provisions for mitigating circumstances such as instigation by a voluptuous, scantily clad vixen showing up at an all boys' parochial school picnic outing?
• What kind of proof would be required? It would seem that the evidence would be evanescent at best particularly after the suspected perpetrator was notified that he's to be arrested.

I'd be grateful for some legal clarification as a confluence of events might find me in one of the states in question in the state in question.