In Luce v. United States 469 U.S. 38 (1984), the defendant wanted to testify free from impeachment by a prior conviction. The trial court decided the prior conviction was in the category of permissible impeachment evidence and refused to foreclose its use. In declining to review the merits of the alleged error, the United States Supreme Court observed that reviewing the trial court's ruling was fraught with difficulty, requiring speculation about: (1) the precise nature of the defendant's testimony; (2) whether the trial court's ruling would have remained the same or would have changed as the case unfolded; (3) whether the government would have sought to impeach the defendant with the prior conviction; (4) whether the accused would have testified in any event; (5) whether any resulting error in permitting impeachment would have been harmless. The Court held that to raise and preserve for review the claim of improper impeachment with a prior conviction, a defendant must testify. The United States Supreme Court held that a defendant who did not testify would not be allowed to appeal an in limine ruling that permitted use of a prior conviction for impeachment purposes under Federal Rule of Evidence 609(a). In Luce, the Supreme Court left this question open, noting that its ruling dealt with a preliminary ruling "not reaching constitutional dimensions," Luce, 469 U.S. at 43; and a concurring opinion acknowledged that if a constitutionally based objection to the impeachment evidence were presented, "the calculus of interests" might be different. Id. at 44 (Brennan, J. concurring). The Supreme Court held that a defendant must testify in order to preserve for review a claim of improper impeachment. In Luce, the trial court balanced the probative value of a prior conviction against the prejudicial effect to the defendant and on appeal the Supreme Court held that "to perform this balancing, the court must know the precise nature of the defendant's testimony, which is unknowable when, as here, the defendant does not testify." Id. at 41, 105 S. Ct. at 463. The Supreme Court identified several problems with review under such circumstances: the ruling would be subject to change depending on the defendant's testimony at trial; the reviewing court has no way of knowing how and if the government would have used the impeachment evidence; the reviewing court cannot assume that the defendant's decision not to testify was based on the adverse ruling; and the reviewing court has no way of determining whether the district court's in limine ruling was harmless error. Id. at 42, 105 S. Ct. at 463. The Supreme Court held that "to raise and preserve for review the claim of improper impeachment with a prior conviction, a defendant must testify," and identified a "litany of policy reasons" supporting the rule. First, the Court noted that without the defendant's testimony, a reviewing court is "handicapped" in weighing the probative value of a prior conviction against the prejudicial effect to the defendant. Luce, 469 U.S. at 41. Second, any possible harm is "wholly speculative" because the trial court's ruling is subject to change as the case unfolds and the reviewing court has no way of knowing if the prosecutor actually would have sought to impeach with the prior conviction. Id. at 41-42. Moreover, because a defendant's "decision whether to testify seldom turns on the resolution of one factor, a reviewing court cannot assume that the adverse ruling motivated a defendant's decision not to testify." Id. at 42. Finally, the Court pointed out that, in this situation, a reviewing court cannot determine if any error is harmless because it "could not logically term 'harmless' an error that presumptively kept the defendant from testifying." Id. The United States Supreme Court held "that to raise and preserve for review the claim of improper impeachment with a prior conviction, a defendant must testify." The Supreme Court set out three reasons for its holding. First, appellate courts are "handicapped" in reviewing evidentiary questions outside a factual context. ( Id. at p. 41.) In particular the decision to admit evidence of prior convictions requires balancing probative value against prejudicial effect. (Fed. Rules Evid., rule 609(a)(1), 28 U.S.C.) To perform this balancing a court must know the precise nature of the defendant's testimony, which is unknowable when the defendant does not testify. Second, any possible harm flowing from an in limine ruling permitting impeachment by prior convictions is "wholly speculative." (Luce, at p. 41.) The trial court might revise its ruling on an in limine motion as the evidence unfolds, or the prosecution may ultimately choose not to impeach with the prior convictions. ( Id. at pp. 41-42.) Third, if defendant does not testify, it is difficult to measure the harm caused by any error. "Were in limine rulings under Federal Rules of Evidence Rule 609(a) reviewable on appeal, almost any error would result in the windfall of automatic reversal; the appellate court could not logically term 'harmless' an error that presumptively kept the defendant from testifying." ( Id. at p. 42.) A unanimous Supreme Court announced the rule: "To raise and preserve for review the claim of improper impeachment with a prior conviction, a defendant must testify." The court gave three reasons for the rule. The primary concern was that, "A reviewing court is handicapped in any effort to rule on subtle evidentiary questions outside a factual context." (Id. at p. 41.) First, the trial court could not weigh the probative value of the prior conviction evidence against its prejudice unless it knew the "precise nature" of defendant's testimony. (Ibid.) An offer of proof was insufficient. (Id. at p. 41, fn. 5.) Second, any possible harm from the ruling is wholly speculative. As the case unfolds, the prosecutor might decide not to use the impeachment evidence. (Id. at p. 41.) Third, when the trial court erred, the reviewing court could not weigh the prejudice, thus, such errors would result in a windfall of automatic reversal. (Id. at p. 42.)