Although sparse United States Supreme Court dicta and precedent suggest that nonconstitutional privilege rules may have to yield to a criminal defendant's federal constitutional rights, except for the specific and rare circumstances in which the Court has said or suggested that must happen, it is unknown when such privilege rules must yield to a criminal defendant's constitutional rights such as the right to compulsory process and the broader federal constitutional right to present a defense in a criminal trial.

Fed. R. Evid. 103(d) advisory committee's note ("This wording of the plain error principle is from Rule 52(b) of the Federal Rules of Criminal Procedure. While judicial unwillingness to be constructed by mechanical breakdowns of the adversary system has been more pronounced in criminal cases, there is no scarcity of decisions to the same...The plain error rule in Federal Rule of Evidence 103(d), which can relieve a party from the obligation to make a satisfactory offer of evidence or a satisfactory objection, does not operate only in favor of criminal defendants; it can, for example, benefit a party in a civil action.

Cf. O'Brien v. Marshall, 453 F.3d 13, 19 (1st Cir. 2006) (holding, in a habeas corpus petition, that the "[petitioner] was not denied the use of compulsory process, but, as with the Fifth Amendment," because the....The Due Process and Compulsory Process guarantees give a defendant in a federal or state criminal trial the constitutional right, not only to compel the attendance of defense witnesses, but also to introduce trustworthy hearsay evidence that is critical or important to the defendant's defense.

Cf. United States v. Glenn, 312 F.3d 58, 70 (2d Cir. 2002) (footnotes omitted: "Circumstantial evidence can be as compelling as direct evidence and a conviction can rest solely on circumstantial evidence. But the jury must have been presented with a sufficient evidentiary predicate to support the...Inferences based on inferences are permissible