The central concern of the Confrontation Clause is to ensure the reliability of the evidence against a criminal defendant by subjecting it to rigorous testing in the context of an adversary proceeding before the trier of fact. The word "confront," after all, also means a clashing of forces or ideas, thus carrying with it the notion of adversariness.
the right guaranteed by the Confrontation Clause includes not only a "personal examination," 156 U.S. at 242, but also "(1) insures that the witness will give his statements under oath--thus impressing him with the seriousness of the matter and guarding against the lie by the possibility of a penalty for perjury; (2) forces the witness to submit to cross-examination, the 'greatest legal engine ever invented for the discovery of truth'; [and] (3) permits the jury that is to decide the defendant's fate to observe the demeanor of the witness in making his statement, thus aiding the jury in assessing his credibility."
The central issue in determining whether the Confrontation Clause is implicated is whether the proffered statement is "testimonial" or "nontestimonial." If the court determines the proffered statement is non-testimonial, the Confrontation Clause is not implicated. Instead, the court should determine the admissibility of the non-testimonial statement under traditional hearsay rules. If, however, the court determines a statement is testimonial, the Confrontation Clause is implicated. Accordingly, the statement shall be excluded unless the witness is unavailable and the opposing party had an opportunity to cross-examine the witness. The key to determining whether a statement is testimonial or non-testimonial depends on the primary purpose of the statement.
The court must determine, based on an objective review of the surrounding facts and circumstances, whether the primary purpose of the statement was to aid the police during an ongoing emergency or whether the primary purpose of the statement was to prove past events. The United States Supreme Court held that there is a key, temporal difference between testimonial statements and non-testimonial statements. Non-testimonial statements answer the question "what is happening." Testimonial statements, on the other hand, answer the question "what happened." The primary purpose test is as follows:
A statement is non-testimonial "if it is made with the purpose of enabling police to meet an ongoing emergency.
Conversely, a statement is testimonial "if it is made in the absences of an ongoing emergency and the primary objective of the interrogation or questioning that resulted in the statement was to establish or prove past events.