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; having charges dropped in exchange for testimony, despite a specific denial that dropping the charges had any effect on the testimony; 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