A trial court has discretion to determine the proper scope of cross-examination to impeach a witness. See Rogers v. State, 93 Wis. 2d 682, 689, 287 N.W.2d 774 (1980). Moreover, as the supreme court has emphasized: "The bias or prejudice of a witness is not a collateral issue and extrinsic evidence may be used to prove that a witness has a motive to testify falsely. The extent of the inquiry with respect to bias is a matter within the discretion of the trial court." State v. Williamson, 84 Wis. 2d 370, 383, 267 N.W.2d 337 (1978). We will not reverse a trial court's discretionary decision to permit cross-examination to expose a witness's possible motive to lie unless the court's decision "represents a prejudicial erroneous exercise of discretion." State v. Lindh, 161 Wis. 2d 324, 348-49, 468 N.W.2d 168 (1991), reversed sub nom. Lindh v. Murphy, 521 U.S. 320, 138 L. Ed. 2d 481, 117 S. Ct. 2059 (1997).