[greymule]

I would not call an out for interference on the grounds that the catcher had to throw over or around the runner. I would tell my fielders to play the ball normally and expect an interference call if they hit the runner with their throw. (Of course, that's asking a lot!)

Even if a runner is not hit by the throw, she can still interfere, for example, by blocking the vision of the fielder taking the throw or even by colliding with the fielder outside the lane.

I've had catchers simply not throw the ball at all and then look at me in frustration. But there certainly can't be interference without a throw. In fact, it should be a quality throw, which pretty much rules out wild ones.