Cross-examination
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; 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.
Read more about this topic: Confrontation Clause