I've done some googling, and can't find any instances were a journalist was actually convicted. All I can find is instances that they weren't charged or charges were dropped.
Several of these cases involved a blogger(or other small syndication) confronting police who were responding to an incident. You don't have to look far to see these encounters on youtube. I'm not justifying the police in these situations, however the "journalists" were doing much more than observing; bordering on obstruction.