There are several times in a trial when I might ask the judge for a no contact order, to sequester witnesses, or to prohibit witness contact during a break or recess in the trial.
I have a fairly standard format for rape and child abuse cases. These in my experience are the cases where the opportunity for witness contamination is at its apogee. Oftentimes you are arriving on the scene too late as the defense counsel because most of the damage has already been done. However, you should still be attempting to minimize damage. For the moment though I wanted to focus on what happens in trial when there is a break in the trial and a witness is still on the witness stand either for their direct, their cross-examination, their redirect, or might be back for rebuttal. And this point works both ways — for defense and for government.
My personal belief is that once someone has begun their testimony no-one should talk to them and they should be told by the judge not to talk with anyone, including talking with the lawyer who called them. I always ask that of the judge when a prosecution witness is involved, and I always tell that to my own witnesses if it happens to us. There are too many ways subtle and not so subtle that a person can respond to the "how am I doing question," for example.
So in this context we can revisit Mil. R. Evid. 615, as well as look at Fed. R. Evid. 615, in the context of Guthrie. Here is the link and blurb from Federal Evidence Review.
permitting contact with the victim witness during an overnight recess,
and where no improper or prejudicial contact was shown, in United States v. Guthrie, _ F.3d _ (6th Cir. 2009) (Nos. 07-6215, 07-6286).
In that case the defense was given the opportunity the next morning to have liberal examination to explore any potential improprieties that happened overnight, such as coaching. The defense did not cross-examine into that and there was no evidence anything untoward happened overnight. Perhaps the sensible prosecutor stayed at arms length from the witness to avoid even the appearance of impropriety.
Now take a look at United States v. Rodriguez-Rivera, 63 M.J. 372 (C.A.A.F. 2005). The issue of coaching was resolved against the appellant. They all decided that all that happened was that the child witness was told to tell the truth and the whole truth. What the court and parties don't necessarily get is that the message sent to the child was trial counsel and parental dissatisfaction with the testimony so far. The message to the child who wants to please is to add more information, apparently new information. The witness asked specifically, "whether she had done something wrong?" The answer she got back was "yes." Oh not directly, but when the witness is then counseled to tell the truth, isn't it just as likely that the witness is responding to being told that she's doing something wrong, and now wants to please so that she's not in trouble? Rodriquez-Revera, 63 M.J. at 377.
You also have to account for the exception to sequester rules for alleged victims.
In my view, shared happily by most judges, a victim can still be sequestered until such time as they are no longer going to testify, and thus have their testimony shaped deliberately or incidentally. So, if the alleged victim testifies and the prosecutor tells the judge — on the record — that the witness isn't going to testify, even in sentencing, I don't think they can be excluded at that point. That is so even though the alleged victim has a chance to hear testimony and potentially repeat and discuss it with other witnesses.
The Army TJAG has a comparison chart for the Fed. and Mil. R. Evid. at the end of the Basic Course book on Evidence.