State v. Allred (1982)
In State v. Allred, 134 Ariz. 274, 277, 655 P.2d 1326, 1329 (1982), the Arizona Supreme Court acknowledged the danger of unfair prejudice when impeachment evidence is used for substantive purposes.
One factor to consider in determining unfair prejudice is whether the impeachment testimony is the sole evidence of guilt. Id.
The court concluded that where the impeachment evidence "was a pretense for substantive use of an otherwise inadmissible . . . statement" and, if admitted, the statement "would form the only evidence that the crime was committed" by the defendant, "the danger of unfair prejudice and unjust determination is so great" as to require vacating the defendant's conviction on that charge. Id. at 278, 655 P.2d at 1330.