[UmpJM]

Trigger,

Sitch 1: If the F6 is in the "act of fielding" the pick-off throw, he may be in a position that blocks the runner's access to the base. If he is not, and hinders the runner return to the base, he is guilty of obstruction - possibly Type A obstruction, which would result in the obstructed runner being awarded 3B. He is also liable to receive some cleats or a shoulder to his ankle (or whatever) with some degree of force. Whether he was in the act of fielding and whether the runner was hindered is solely a matter of umpire judgement.

Sitch 2: Delayed dead ball. If the catcher's throw results in the stealing runner being retired, the play stands and the interference is disregarded. If the runner is not retired on the throw, the batter is out and the runner returns.

JM