Parties may 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. 413(d) ("For purposes of this rule and Rule 415, "offense of sexual assault" means a crime under Federal law or the law of a State (as defined in section 513 of title 18, United States Code) that involved-- (1) any conduct proscribed by chapter 109A of title 18, United States Code; (2) contact, without consent, between any...Federal Rule of Evidence 413(d) provides that for purposes of Rule 413 and also for purposes of Federal Rule of Evidence 415 an "offense of sexual assault" is a crime under Federal law or the law of a State (as defined in section 513 of title 18, United States Code) that involved-- (1) any conduct proscribed by chapter 109A of title 18, United States Code; (2) contact, without consent, between any part of the defendant's body or an object and the genitals or anus of another person; (3) contact, without consent, between the genitals or anus of the defendant and any part of another person's body; (4) deriving sexual pleasure or gratification from the infliction of death, bodily injury, or physical pain on another person; or (5) an attempt or conspiracy to engage in conduct described in paragraphs (1)-(4).

Wilborg v. United States, 163 U.S. 632, 658 (1896).An objection is unnecessary to preserve a claim of error and a trial court should exclude, on its own initiative, evidence offered against a criminal defendant or other disadvantaged party when admission of the evidence would be "plain error."

United States v. Jennings, 496 F.3d 344, 349-350 (4th Cir. 2007) (upholding trial court's admission of testimony of two passengers [about the statements of the 13-year old girl on what had occurred on the flight] as excited....A statement falls within the hearsay exception created by Federal Rule of Evidence 803(2) or a comparable State rule for excited utterances, only if the declarant (the maker of the statement) was under the stress of the startling event or condition when he or she made the statement that relates to that startling event or condition.