Originally Posted by v205
If you are closest to the ball and you are not sure either way. Play it as IN.
NOPE, not really a good rule of thumb. Quite often, the player closest to the ball has the worst vantage point, not the best as many people assume. If you are too close to the bounce event, your eyes cannot track the ball accurately. In these situations, that player's partner often has a better vantage point. Even the opponents may have a better vantage point than a player that is too close to the ball.
Quite often a player is focused on either the ball or on an expected contact zone and not on the lines at all. Often, that person cannot make an accurate call.
On the other hand, if their eyes & head are still and they are focused on the line, they can make an accurate call but may be unable to make a clean contact, if needed. I spoke a lot about these matters on page 1 of this thread: