He was doing his act near a window with the curtains/blinds/whatever in an open position. This suggests at best he was absent minded, at worst he intended to show the world.

The police shone a flashlight into his living room, and he then turned out the lights and left the room. Doesn't sound like there was a lot of light in the room - it is a wonder he could be seen at all.

The end claims the definition of a public place was expanded to include the area where a witness is physically located. He was in his living room, they were in their bedroom. I guess for a short time everyone's bedroom was considered a public place?

Since they used a telescope and binoculars to observe the man from a hidden location through a window, they were "peeping toms" and should be treated accordingly. It would have been different if they had been taking the trash to the curb and been able to witness the act.

I don't condone the actions of the accused, but I think he really got spanked on this one. (sorry, couldn't resist)