Even where the witness is unavailable, the defendant usually has a right to cross-examine the witness. An exception to this rule, forfeiture by wrongdoing, is discussed below. The more obvious violations of the right to cross-examine witnesses are those where the defendant has never had the opportunity to cross-examine the witness at all, in any setting, or on any subject. The closer cases are those where some cross-examination has occurred, either at trial or prior to trial. Generally, having the opportunity to cross-examine a witness at trial will satisfy the Confrontation Clause's guarantee. And trial courts are given "broad discretion ... to preclude repetitive and unduly harassing interrogation." The Supreme Court has emphasized that the "Confrontation Clause guarantees an
opportunity for effective cross-examination, not cross-examination that is in whatever way, and to whatever extent, the defendant might wish. Nonetheless, a trial court cannot preclude cross-examination on some subjects. Besides the subject matter of the case, the crime for which a defendant is charged, a defendant has the right to attack the credibility or impeach the testimony of the witness. Despite trial courts' "broad discretion", it is an error to limit defendants from cross-examining witnesses on an area that would expose a "prototypical form of bias" that would be relevant to the jury's assessment of that witness's credibility. Examples of such biases include being on probation as a juvenile delinquent, even where the state normally considers such a status to be protected confidential information; and shared allegiances of the victim and witness, including gang membership. In
Crawford v. Washington, , the Supreme Court increased the scope of the Confrontation Clause by ruling that "testimonial" out-of-court statements are inadmissible if the accused did not have the opportunity to cross-examine that accuser and that accuser is unavailable at trial. In
Davis v. Washington , the Court ruled that "testimonial" refers to any statement that an objectively reasonable person in the declarant's situation would believe likely to be used in court. In
Melendez-Diaz v. Massachusetts, , and
Bullcoming v. New Mexico, , the Court ruled that admitting a
lab chemist's analysis into evidence, without having him testify, violated the Confrontation Clause. In
Michigan v. Bryant, , the Court ruled that the "primary purpose" of a shooting victim's statement as to who shot him, and the police's reason for questioning him, each had to be
objectively determined. If the "primary purpose" was for dealing with an "ongoing emergency", then any such statement was not testimonial and so the Confrontation Clause would not require the person making that statement to testify in order for that statement to be admitted into evidence. == Exceptions to the right of confrontation ==