The Compulsory Process Clause of the Sixth Amendment to the U.S. Constitution gives a defendant in a criminal trial a constitutional right to compel a person who may have probative and material evidence to testify.

United States v. Bailey, 270 F.3d 83, 87 (1st Cir. 2001) (upholding trial court's admission of agent's testimony about defendant's actions following her agreement to cooperate because it did not constitute hearsay....If some human utterance has legal significance under applicable substantive law and the utterance is offered to establish that a verbal act having such legal significance has taken place, the utterance is not hearsay under Federal Rule of Evidence 801(c) or a "statement" for purposes of Federal Rule of Evidence 801(a)(2) even if the utterance also contains an assertion or appears to contain an an assertion.

Fed. R. Evid. 404(b) (Evidence of other crimes, wrongs, or acts "may...be admissible for other purposes, such as proof of ... preparation, plan....").Evidence of another crime, wrong, or act is not barred by the prohibition against circumstantial use of character if such other crime, wrong, or act is offered to prove the existence of a plan or scheme.

United States v. Thomas, 453 F.3d 838, 844 (7th Cir. 2006) (upholding trial court's admission of the tape-recorded 911 call which did not violate defendant's rights under the Confrontation Clause because "the anonymous....The right of confrontation guaranteed by the Confrontation Clause of the Sixth Amendment to the U.S. Constitution puts no constraints on the admissibility of nontestimonial hearsay statements; the federal constitutional right of confrontation does not apply to such statements.