I'm an attorney and, although I practice on the Civil side, I have never seen a witness who did not discuss his upcoming testimony with the attorney who would be calling him. Such non-party witnesses are routinely excluded from the actual testimony and they may be cross-examined as to conversations with the opposing attorney. Such conversations do not comprise grounds for dismissal. This must be a local or personal Rule of this judge.
Thanks. Every insight by an attorney posted on this thread is helpful -- to me, at least.