I think just saying PR (vs which PR) is sufficient, and shouldn't weaken the scum team...
Not sure how you plan to 'inform' witnesses and if you're just going to give cryptic clues (vs. flat out naming the day-killer), but you might consider giving the town a watcher role instead.
Make them strictly a 'day-watcher' in that they only have power during the day. On each day, they choose one person to watch. If that 'watched' person performs an action (or has one performed on them) the watcher is notified...
Examples:
If the watcher watches player A, and player D day-kills player A, then in addition to to the mod reporting the death scene in the thread, the watcher receives a PM saying 'Player A was visited by Player D'.
If the watcher watches player D, and player D day-kills player A, then in addition to the mod reporting the death scene in the thread, the watcher receives a PM saying 'Player D visited Player A'.
If nothing happens with the watched player, the watcher receives a PM saying 'Nothing to report'.
With the watcher role there's a chance of a witness to any day-kill, but not a guarantee.
Just a thought.