File under: Yeah, thanks for "helping".
Anthony A. Payne, Maryville, was shot with a taser. One dart landed in his left eyeball. The officer (Blount County Sheriff) even cycled the taser a second time to make sure. Payne's eye was obviously damaged beyond repair. A lawsuit has been launched. [LINK]
In my opinion (based only on the linked report), this would only be acceptable if Mr. Payne was charging towards the officer with a knife. In such cases, he'd be fair game. But if Mr. Payne was just sitting there, sad and depressed, then attacking him with a dangerous weapon was uncalled for.