Crawford v. Washington, has adopted a testimonial approach to the Confrontation Clause of the Sixth Amendment. Under this approach, a statement that is deemed to be testimonial in nature may not be introduced at trial against an accused unless he has had an opportunity to cross-examine the person who made the statement and that person is unavailable to testify at trial. If a statement is not deemed to be testimonial, then the Confrontation Clause poses little if any obstacle to its admission.2 A great deal therefore now rides on the meaning of the word "testimonial."
Friedman, Richard D. "Grappling with the Meaning of 'Testimonial'." Brook. L. Rev. 71, no. 1 (2005): 241-80.