[Dave Brost]

Some good points made about answering for your partner. I have trouble with this, and feel like I am short-changing my partner if I say "it wasn't my call", but at the same time do not want to be answering for something I might not have all the right facts to answer.
As for making a call in your partners area, it was not stated clearly what the situation was, but I always discuss in our pre-game that if the trail is in good position to see a play that is in the leads area, go ahead and make the call. The lead may be screened from a reach-in the happens in the paint. If I am the trail and have dropped down to a good position, I would make the call if I had one.
Make it clear though, that I am not going to make calls in my partners area, when I have my own area to cover. In the situation above, this is a grey area where we might both be observing. The key is that I was in good position to see it. A coach will not argue the fact of position if your are there. He still might not like the call though.