Oswalt (D) was charged with robbery as a result of an incident which occurred on July 14 in Washington. D's defense was alibi. He presented Ardiss as a witness. Ardiss testified that D was a regular patron of his restaurant in Oregon and that D was in the restaurant on July 14, rendering it impossible for D to have been in Washington at the time of the robbery. On cross-examination, Ardiss testified that D had been in the restaurant every day during the months surrounding the incident. To rebut this testimony, the state was allowed to present a police officer who testified that he had seen D in Washington on June 12. D objected to this testimony, arguing that his presence in Washington on June 12 was not in issue. The state argued that it was admissible to challenge the witness' credibility and to establish D's presence in Washington preparatory to the offense.