Seems to me that the best practice is to raise any possible UCI claims prior to trial on the merits–depending on when you learn of the alleged UCI.
The general rule is the defense does not waive UCI by failing to raise it at trial. Id. at 193. This rule, however, is not absolute. The United States Court of Appeals for the Armed Forces (CAAF) has distinguished UCI in the accusative phase (e.g., involving the preferral, forwarding, and referral of charges), from UCI in the adjudicative phase (e.g., interference with witnesses, judges, members, and counsel). United States v. Weasler, 43 M.J. 15, 17-18 (C.A.A.F. 1995). In making this distinction, the CAAF concluded claims of UCI during the accusative phase can be waived. Id. at 19 (“Where there is coercion in the preferral process, ‘the charges are treated as unsigned and unsworn,’ but the ‘failure to object’ constitutes waiver of the issue.”). The court has also found waiver of defects in the forwarding process if not challenged at trial. Id. (citing United States v. Hamilton, 41 M.J. 32, 36 (C.M.A. 1994)).
Having concluded referral is part of the accusatorial stage, we examine appellant’s knowledge of the facts at the time and whether appellant was in some way precluded from raising UCI at trial. “If command influence is known, or reasonably could be known in either the accusatorial stage or the selection process, failure to raise the issue constitutes waiver.” See United States v. Upshaw, 49 M.J. 111, 114 (C.A.A.F. 1998) (Crawford, J., concurring) (citing Weasler, 43 M.J. at 17).