Can parties agree, both before and during trial, to waive, forfeit, or modify the rules of evidence that apply in trials to which they are or may become parties?

Fed. R. Evid. 803(18) ("To the extent called to the attention of an expert witness upon cross-examination or relied upon by the expert witness in direct examination, statements contained in published treatises, periodicals, or pamphlets on a subject of history, medicine, or other science or art, established as a reliable authority by the...If a treatise, periodical, or similar literature is shown to be reliable and authoritative on a topic, under some circumstances a statement in such literature about the topic falls within an exception to the prohibition against the admission of hearsay evidence.

United States v. Rainone, 32 F.3d 1203, pin? (7th Cir. 1994) (opinion by Judge Posner for the court; under the circumstances court rejects attack on use of attorney-client privilege to shield notes of co-defendant's communications with his attorney; however, under other...Although United States Supreme Court precedent establishes that in some circumstances a nonconstitutional privilege must yield to the federal constitutional rights of a criminal defendant, apart from the specific circumstances for which the Court has given an authoritative answer, it is unsettled and and it is unknown when such a privilege rule must yield to a federal constitutional right such as confrontation, due process, or the right to present a defense.

Estelle v. McGuire, 502 U.S. 62, 69 (1991) ("The prosecution must prove all the elements of a criminal offense beyond a reasonable doubt.").The prosecution must establish each essential element of a criminal offense beyond a reasonable doubt.