IS or IP?

[dumbref]

Originally Posted by mcrowder

It was IP BEFORE he moved toward the play, and then became super-secret-double-probation IP after he moved.

IS can only be applied in a situation like this if the player in question had NO POSSIBLE EFFECT on the play.

Would you call a block in the back because he possibly blocked in the back. Why should we call IP because he possibly had an effect on the play? Shouldn’t we have to see what that effect was before calling IP?