Cross-examination is ordinarily the examination of a witness by a party who is opposed to the party who first called that witness. So, for example, if the prosecution calls a police officer first to testify, when the defendant's Lehigh County criminal lawyer asks questions of the police officer, that police officer would be under cross examination a want of prejudice would cure it . This was outlined in 1987 in the case of Commonwealth v. Erie.
The right of cross examination extends beyond the subjects to which the witness testifies on direct examination, and includes the right to examine a witness on any fact tending to refute inferences or deductions arising from matters testified to on direct examination. A defendant places his reputation for honesty at issue merely by taking the stand, and the defendant's credibility may be impeached by reputation evidence. The rationale for this impeachment rule is that if a defendant offers himself as a person worthy of belief, the jury has a right to know what kind of man he is as an aid in assessing his credibility.
The scope of cross-examination is largely within the discretion of the trial judge, and in setting the limits of cross-examination the trial court may consider the extent that a jury would be confused by testimony. Thus, the trial court may limit the scope of cross-examination to prevent repetitive inquiries and cumulative testimony. Even if the courts ruling is erroneous, the error will not be a ground for reversal unless it results in an "apparent injury".
Cross-examination is generally limited to matters brought out on direct examination. However, an exception exists when the cross examiner is seeking to show bias on the part of the witness. Whatever tends to show the interest or feeling of the witness in a cause is competent, because the right to confront a witness includes the right to cross-examine a witness about possible motives to testify. For example, a defendant had a right to cross-examine the victim who was her former landlord on his allegations that she had stolen from him and a codefendant, had shut off their utilities, and that she was serving a prison sentence for having thrown a chemical at a codefendant. It was determined to be error to preclude cross examination of a complaining about favorable treatment anticipated or received from the Commonwealth in exchange for their testimony. This is done frequently in the movies, when you have an inside rat or snitch testifying against a friend, fellow inmate, or someone else in their gang for a more lenient sentence.
A witness may also be cross-examined about pending criminal cases when the witness' possible bias arises from hopes for leniency. In Commonwealth v. Butler from 1987, it was determined by the Superior Court that it was reversible error to prevent the defendant from showing that a police officer's testimony was biased because he was a defendant in a civil suit alleging and unconstitutionally introduces body cavity search. A witness may be cross-examined by defense counsel as to his address and occupation, even if that elicits evidence that the witness had been incarcerated for an unrelated crime. Such evidence identifies the witness with his environment, and they also show that the testimony was affected by fear or favor growing out of his detention. Failure to allow this cross-examination is reversible error. Communications protected by privileges such as those between spouses, between attorney and client, or between a pastor and parishioner, may not be the subject of cross examination. However, the witness must be compelled to assert the privilege before the jury.