(dissenting).
For good reason, courts have long followed the rule against admitting bad-acts evidence “for the purpose of showing that the defendant has a criminal disposition in order to generate the inference that he committed the crime with which he is charged.” United States v. Myers, 550 F.2d 1036, 1044 (5th Cir.1977). As the court in Myers observed, “[a] concomitant of the presumption of innocence is that a defendant must be tried for what he did, not for who he is.” Id. This rule is “fundamental to American jurisprudence.” United States v. Foskey, 636 F.2d 517, 523 (D.C.Cir.1980).
Courts also recognize the critical importance of guarding against incursions on the rule, not because bad-acts evidence has no probative value, but for the very reason that such evidence may have very substantial probative value not recognized in law. United States v. Goodwin, 492 F.2d 1141, 1155 (5th Cir.1974). Therefore, “[t]he exclusion of bad-acts evidence is founded not on a belief that the evidence is irrelevant, but rather on a fear that juries will tend to give it excessive weight, and on a fundamental sense that no one should be convicted of a crime based on his or her previous misdeeds.” United States v. Daniels, 770 F.2d 1111, 1116 (D.C.Cir.1985). Empirical studies have confirmed that juries treat such evidence as highly probative. Id.; see also State v. Most, 578 N.W.2d 250, 254 (Iowa Ct.App.1998) (“In any case where prior crimes evidence is offered, the court must consider the strong tendency for the jury to use it for an improper purpose.”).
Bad-acts evidence “diverts the attention of the jury from the question of defendant’s responsibility for the crime charged to the improper issue of his bad character.” United States v. Phillips, 401 F.2d 301, 305 (7th Cir.1968). Consequently, even if the trial judge gives a carefully crafted instruction limiting the significance of such evidence, prejudice to the defendant is “well-nigh inescapable.” United States v. Carter, 482 F.2d 738, 740 (D.C.Cir.1973). The rule against bad-acts evidence is therefore “ ‘just and wise’ in order to avoid the enormous danger of prejudice to the defendant that [such evidence] creates.” United States v. San Martin, 505 F.2d 918, 921 (5th Cir.1974).
Finally, courts recognize
that the various categories of exceptions [to the bad-acts evidence] — intent, design or plan, identity, etc. — are not magic passwords whose mere incantation will open wide the courtroom doors to whatever evidence may be offered in their names. To the contrary, each exception has been carefully carved out of *249the general rule to serve a limited judicial and prosecutorial purpose.
Goodwin, 492 F.2d at 1155. These exceptions, courts have cautioned, “should not be permitted to swallow the rule.” San Martin, 505 F.2d at 921 (quoting United States v. Miller, 500 F.2d 751, 762 (5th Cir.1974)).
Our Rule of Evidence 404(b) controls the admissibility of bad-acts evidence. It provides:
Evidence of other crimes, wrongs, or acts is not admissible to prove the character of a person in order to show that he acted in conformity therewith. It may, however, be admissible for other purposes, such as proof of motive, opportunity, intent, preparation, plan, knowledge, identity, or absence of mistake or accident.
Iowa R. Evid. 404(b).
Consistent with the foregoing authority, we have noted that rule 404(b)
recognizes two fundamental principles: first, that evidence of other bad acts is relevant to whether a defendant committed the charged crime, and second, the reality that such evidence, while highly probative, is also highly prejudicial to a defendant. The rule attempts to balance these competing interests by presuming that the [bad-acts] evidence is inadmissible and placing the burden on the State to show the evidence is relevant for some purpose other than to show the defendant acted in a manner conforming to the other bad acts. See State v. Cott, 283 N.W.2d 324, 326 (Iowa 1979) (“The purpose of the rule is to exclude from the jury’s consideration evidence which has no relevancy except to show the defendant is a bad person and thus likely committed the crime in question.”).
State v. Mitchell, 633 N.W.2d 295, 298 (Iowa 2001).
The listed exceptions in rule 404(b) are not exclusive. Id. The critical issue is “whether the disputed evidence is ‘relevant and material to some legitimate issue other than a general propensity to commit wrongful acts.’ ” Id. (quoting State v. Barrett, 401 N.W.2d 184, 187 (Iowa 1987)). “If the challenged evidence is relevant to a legitimate issue in dispute, then it is prima facie admissible, regardless of any tendency to also establish a defendant’s bad character or propensity for committing bad acts.” Id. However, courts do not look with favor upon bad-acts evidence and its use “must be narrowly circumscribed and limited.” United States v. Hodges, 770 F.2d 1475, 1479 (9th Cir.1985) (quoting United States v. Bailleaux, 685 F.2d 1105, 1109 (9th Cir.1982)).
To determine whether such disputed evidence is admissible, courts engage in a two-step process. Mitchell, 633 N.W.2d at 298. First, the court must determine whether the bad-acts evidence is relevant to a legitimate factual issue in dispute. Id. If the court determines such relevancy exists, it then decides whether the probative value of the bad-acts evidence is substantially outweighed by the danger of unfair prejudice to the defendant. Id.; Iowa R. Evid. 403. An affirmative finding in this balancing process overcomes the evidence’s prima facie admissibility. Mitchell, 633 N.W.2d at 298. The court must then exclude the evidence. Id. However, in employing this two-step process, courts must keep in mind that bad-acts evidence “must be carefully scrutinized to determine probative value.” United States v. Back, 588 F.2d 1283, 1287 (9th Cir.1979).
As the majority states, each step invokes the district court’s discretion. But that discretion has parameters:
It should be recognized, however, that this is not a discretion to depart from the principle that evidence of other *250crimes, having no substantial relevancy except to ground the inference that accused is a bad man and hence probably committed this crime, must be excluded. The leeway of discretion lies rather in the opposite direction, empowering the judge to exclude the other-crimes evidence, even when it has substantial independent relevancy, if in his judgment its probative value for this purpose is outweighed by the danger that it will stir such passion in the jury as to sweep them beyond a rational consideration of guilt or innocence of the crime on trial. Discretion implies not only leeway but responsibility. A decision clearly wrong on this question of balancing probative value against danger of prejudice will be corrected on appeal as an abuse of discretion.
Mitchell, 633 N.W.2d at 299 (quoting State v. Johnson, 224 N.W.2d 617, 621 (Iowa 1974)).
My disagreement with the majority stems from the required balancing process stated in rule 403. I will therefore focus my discussion on that process as it relates to this case and point out the flaws that I think require reversal because of an abuse of discretion.
I begin by noting that
[wjhile trial courts have discretion in striking the balance between probative value and unfair prejudice ... they must be particularly sensitive to the potential prejudice that is always inherent in evidence of an accused’s prior uncharged crimes or wrongs.... Although Rule 403 provides broad umbrella protection from unfair or undue prejudice, the specific provision of Rule 404(a) prohibiting evidence of unclnirged crimes to show bad character or tendencies toward criminality not only reflects the special danger of other crimes evidence but should alert trial courts to be particularly careful in admitting such evidence.
United States v. Carleo, 576 F.2d 846, 849 (10th Cir.1978) (citations omitted).
When intending to introduce bad-acts evidence, the State not only has the duty to show the trial court how the proffered evidence is relevant to one or more issues in the case, it must also articulate precisely the applicability of a rule 404(b) exception. See People v. Golochowicz, 413 Mich. 298, 313, 319 N.W.2d 518, 523 (1982) (holding that when requesting admission of bad-acts evidence, prosecutor’s first duty is to specify the rule 404(b) exception upon which the State relies and noting that while in some instances the evidence might be admissible for more than a single purpose, that is not usually the case).
Additionally, the trial court must identify the applicable exception. United States v. Beasley, 809 F.2d 1273, 1279 (7th Cir.1987). A broad statement merely invoking or restating rule 404(b) will not suffice. See Golochowicz, 319 N.W.2d at 523 (holding that trial court should require the prosecutor to “identify the specific basis in the rule justifying its admission”). This requirement not only ensures that a decision to admit or exclude bad-acts evidence will be made only after issues and reasons are exposed and clearly stated, but it also greatly aids an appellate court in its review of these evidentiary issues.
That brings me to the first flaw regarding the rule 403 balancing process in this case. In the hearing on the defendant’s motion in limine to exclude the prior and subsequent bad-acts evidence regarding the assaults, the prosecutor took the “shotgun” approach:
This is a relationship not of real long standing but of some number of — almost a year, something like that, over the course of which a number of violent acts have been perpetrated upon [the victim]. *251We offer those to notice the defendant’s acts ... conform with some kind of bad character or to prove that he must have done this when he did those. Our point is to show his motive, his intent, the lack of mistake, lack of an accident, involved here.
Of course, by his statement, the prosecutor indicated he was using the evidence for the very reason bad-acts evidence is excluded — “to prove his bad character or to prove that he must have done this when he did those.” The prosecutor did not even mention the key issues that the majority emphasizes the disputed evidence was necessary to prove: confinement with the intent to inflict serious injury. Rather than articulate the key issues and the necessary inferences arising from disputed evidence to prove those issues, the prosecutor simply mouthed the various exceptions in rule 404(b).
On this last point, one appellate court observed:
Experience in the trial courtroom and review of trial records on appeal suggests rather ineontrovertibly that, when asked by the trial judge to specify the grounds for admission of similar-acts evidence, prosecutors often loose a “shotgun” fusillade of reasons which typically include most, if not all, of the purposes named in the statute. Such a response hints, of course, if it does not demonstrate, that the prosecutor has an inadequate understanding of the correct application of the rule and is unclear as to precisely why the evidence is or is not admissible.
Golochowicz, 319 N.W.2d at 523-24 (footnote omitted).
The trial court likewise mentioned all of the exceptions the prosecutor mentioned but in addition threw in opportunity, preparation, plan, and knowledge to prove confinement for the kidnapping charge. The court, however, said nothing regarding the intent to commit serious injury. Nor did the court mention whether the evidence was not more unfairly prejudicial than probative of the issues for which the bad-acts evidence was offered. On this point, the court in Golochowicz had this advice for trial courts:
Similarly, trial judges, when admitting evidence of other crimes, should avoid doing so with the vague justification that “I’ll let it in for what it is worth,” or “I’ll allow it to show plan, scheme or system,” when that is the basis suggested by the prosecutor, without requiring a showing by the prosecutor as to how such evidence is relevant to show plan, scheme or system or how plan, scheme or system is material to the case, or, most importantly, whether the evidence, if indeed relevant and material, is not more unfairly prejudicial than probative of the proposition for which it is offered.
Id. at 524.
One of the disturbing things about the trial court’s ruling on the motion in limine is the reason it gave for admitting the subsequent assaults: to bolster the victim’s credibility. Clearly, according to our decision in Mitchell, this was error. See Mitchell, 633 N.W.2d at 299-300 (holding that bad-acts evidence is not admissible to bolster credibility). The majority dismisses admission of this evidence as harmless error because the evidence was not prejudicial. I disagree. For reasons that follow, I think this evidence along with the prior assaults was highly and unfairly prejudicial to the defendant. The trial court’s failure to recognize this prejudice is the second flaw regarding the rule 403 balancing process.
Our cases define “unfair prejudice” in rule 403 as “an undue tendency to suggest decisions on an improper basis, commonly *252though not necessarily, an emotional one.” State v. Plaster, 424 N.W.2d 226, 231 (Iowa 1988) (adopting definition from advisory committee’s note to Federal Rule of Evidence 403). Thus, evidence is unfairly prejudicial when it “appeals to the jury’s sympathies, arouses its sense of horror, provokes its instinct to punish, or triggers other mainsprings of human action [that] may cause a jury to base its decision on something other than the established propositions in the case.” Id. at 231-32 (quoting 1 J. Weinstein & M. Berger, Weinstein’s Evidence ¶ 403[03], at 403-33-40 (1986)).
When jurors hear that a defendant, on earlier occasions, has committed essentially the same bad acts for which the defendant is on trial, “the information unquestionably has a powerful and prejudicial impact.” United States v. Johnson, 27 F.3d 1186, 1193 (6th Cir.1994). And regardless of the stated purpose of such evidence, “the likelihood is very great that the jurors will use the evidence precisely for the purpose it may not be considered” — to convict the defendant because he is a bad person. Id.; see also State v. Daly, 623 N.W.2d 799, 803 (Iowa 2001) (suggesting that admitting evidence of prior convictions for impeachment purposes, which were exactly the same crimes for which defendant was on trial, “could very likely have a substantial effect on a jury, which, although instructed not to do so, could reasonably be expected to misuse the evidence as substantive proof of guilt”).
The prior and subsequent bad acts here involved the same kinds of acts the State was relying on to convict the defendant of the offenses charged. The majority tries to minimize the prejudicial effect of such acts by stating the State did not elicit great detail about the prior bad acts — assaults— and spent a relatively small amount of time on this line of questioning.
As to the prior assaults, the victim testified that the defendant beat her so many times, in private and in public, that she “stopped counting.” She described how on one occasion the defendant put a gun to her head. In describing other incidents of assault, she testified as follows:
Q. Have you suffered any other injuries that we haven’t talked about here so far from him? A. Yes.
Q. What’s the worst? ... A. Where he burned me with a curling iron in my mouth.
[[Image here]]
Q. What kind of injury did that give you that you had to go to the hospital? A. When he took the curling iron off, my whole skin melted and stuck to the curling iron.[Later the victim testified that an argument led to this action during which the defendant tried to strangle her with the curling iron.]
[[Image here]]
Q. Have you had any children by [the defendant]? A. I was pregnant at one time.
[[Image here]]
Q. What happened then? A. ... I told him I was pregnant. We got into a fight. He punched me in the stomach. He just kept on beating me some more to the point where I lost the baby.
As to the assault subsequent to the one in question, the victim testified the defendant “took my money, he ripped up my chain, and when I was walking out the door he tried to pull me back in by the hair.” He also chased her with a knife.
In addition, the victim’s mother testified that she witnessed the defendant’s violent behavior toward the victim during the relationship. The mother testified that she saw black eyes, bruises, and other marks on *253the victim, including the injury to the victim's mouth when the defendant burned her with the curling iron.
I think these acts are so shocking and horrific that the mere mention of them very likely aroused the jury’s sense of horror, provoked its instincts to punish, and caused them to base its decision to convict on these acts rather than on the established propositions in the case. The fact that the prejudicial effect of the evidence of the prior assaults was somehow neutralized by the “equally reprehensible nature of the charged crime” is a red herring. See United States v. Biswell, 700 F.2d 1310, 1319 (10th Cir.1983) (holding that improper admission of bad-acts evidence, even in face of other evidence amply supporting verdict, impinged upon the fundamental fairness of the trial). The fact remains that without the prior and subsequent assault evidence the jury would have had no opportunity to convict the defendant based solely on this evidence. That brings me to the question of whether the probative value of the bad-acts evidence is substantially outweighed by the danger of unfair prejudice.
One authority describes why a balancing test is needed and the factors that go into such a test:
[T]he fact that there is an accepted logical basis for the evidence other than the forbidden one of showing a proclivity for criminality does not preclude the jury from relying on a defendant’s apparent propensity toward criminal behavior. Accordingly, most authority recognizes that the problem is not merely one of pigeonholing, but of classifying and then balancing. In deciding whether the danger of unfair prejudice and the like substantially outweighs the incremental probative value, a variety of matters must be considered, including the strength of the evidence as to the commission of the other crime, the similarities between the crimes, the interval of time that has elapsed between the crimes, the need for the evidence, the efficacy of alternative proof, and the degree to which the evidence will probably rouse the jury to overmastering hostility.
McCormick on Evidence, § 190, at 672-73 (John W. Strong ed., 5th ed. 1999); see also Most, 578 N.W.2d at 254.
This balancing test has been described as “the modern bastion of a long standing tradition that protects a criminal defendant from ‘guilt by reputation’ and from ‘unnecessary prejudice.’ ” United States v. Cook, 538 F.2d 1000, 1004 (3d Cir.1976). And “[bjecause the weighing entails competing interests, it is delicate, and must be employed with care lest accommodation to the prosecutor’s needs results in subverting a principle that is central to our concept of fairness.” Id. Otherwise, we allow the exceptions in rule 404(b) to swallow the important rule. Id.
In the context of this case, I think the two critical factors important to the weighing process, in light of the confinement issue, are the need for the evidence and the efficacy of alternative proof. I disagree with the majority when it says the prior assault evidence was necessary to prove confinement. To begin with, a careful review of the victim’s téstimony regarding the prior assaults does not support an inference that the defendant confined her on the occasions of these assaults.
Therefore, the only reason for such evidence was to show the defendant was a bad person and the jury should convict him because of such acts.
Additionally, the majority concedes the victim’s testimony of the prior assaults was actually needed to bolster the victim’s credibility on the issue of confinement. *254This is an impermissible use of bad-acts evidence. Mitchell, 633 N.W.2d at 299-300.
Finally, there was other proof apart from the prior assaults from which inferences of confinement could be made. See Most, 578 N.W.2d at 254. First, there was the victim’s direct testimony on the issue. Second, her testimony on the issue was bolstered by the testimony of a police officer and her mother as to her physical condition following the assault on October 11. Under the circumstances, the need for the bad-acts evidence was simply not established and its probative value was nominal at best. See Cook, 538 F.2d at 1003 (“The treasured principles underlying the rule against admitting evidence of other crimes should be relaxed only when such evidence is genuinely needed and would be genuinely relevant.”) (quoting United States v. Miller, 500 F.2d 751, 763 (5th Cir.1974)).
To prevent the balancing process from becoming a mechanical process of allowing bad-acts evidence in just because it meets a rule 404(b) exception, there must be a “principled exercise of discretion.” Beasley, 809 F.2d at 1279; see also United States v. Lavelle, 751 F.2d 1266, 1275 (D.C.Cir.1985) (“Introducing evidence of prior bad acts for a legitimate purpose, however, does not automatically cleanse the evidence of its unique quality of unfairly prejudicing the rights of the accused.”). That means the trial judge “must both identify the exception that applies to the evidence in question and evaluate whether the evidence, although relevant and within the exception, is sufficiently probative to make tolerable the risk that jurors will act on the basis of emotion or an inference via the blackening of the defendant’s character.” Beasley, 809 F.2d at 1279; see also Johnson, 27 F.3d at 1193 (“[Bjecause prior acts evidence carries with it such a high risk of confusion and misuse ... there is a heightened need for the careful application of the principles set out in rule 403.”). There was no convincing evidence that that was done here. In fact, the record is barren of any mention by the trial court of any possible prejudice to the defendant. Cf. Daly, 623 N.W.2d at 802.
The trial court’s failure to make an explicit finding on the probative value versus the prejudicial effect of the evidence and its failure to give a limiting instruction highlight the inadequate consideration given to the balancing process. See Johnson, 27 F.3d at 1193; Back, 588 F.2d at 1286. Such failure constitutes still another flaw in the balancing process here. Cf. Daly, 623 N.W.2d at 802 (holding that it was error for trial court not to engage in probative value verses prejudice balancing process under Iowa Rule of Evidence 609 regarding impeachment of criminal defendant for prior conviction).
The final flaw as I see it was the failure of the trial court to give a limiting instruction. Once the trial judge concludes that the balancing weighs in favor of admitting the evidence, the court should ordinarily instruct the jury carefully as to the limited purpose for which the evidence is admitted. United States v. Sangrey, 586 F.2d 1312, 1314 (9th Cir.1978). The advisory committee notes to Federal Rule of Evidence 403 require the trial judge to consider the effectiveness of a limiting instruction in reducing the prejudicial impact of evidence. Such an instruction is the only way to guard against the undue prejudice bad-acts evidence engenders. United States v. Danzey, 594 F.2d 905, 915 (2d Cir.1979). Otherwise the jury is left to its own devices. That usually means the jury will consider such evidence for an improper purpose — to convict based on the bad-acts evidence alone without regard to the limited purpose for which it was introduced.
*255Iowa Rule of Evidence 105 directs that’ when evidence is admissible for one purpose but not admissible for another purpose, “the court upon request shall restrict the evidence to its proper scope and instruct the jury accordingly.” The rule simply means that the court must instruct if requested. It makes no mention about a trial court’s sua sponte obligation to give such an instruction as directed by the advisory committee notes to Federal Rule 403. The majority simply notes that the defendant did not request such an instruction and none was given. That does not answer the question whether the district court should have on its own considered giving the instruction. Given the nature of the bad-acts evidence, I think the only possible way to have avoided unfair prejudice was to give the instruction. Such an instruction, however, still would not have guaranteed the jury would have been able to erase the bad-acts evidence from its collective mind. See Virgin Islands v. Toto, 529 F.2d 278, 282-83 (3d Cir.1976); State v. Castaneda, 621 N.W.2d 435, 442 (Iowa 2001).
I conclude whatever probative value the bad-acts evidence had in this case was substantially outweighed by the danger of unfair prejudice engendered by the admission of such acts into evidence. Given all of the flaws in the balancing process, I conclude the trial court abused its discretion in admitting the evidence. I also conclude the admission of such evidence affected the defendant’s substantial rights and constituted prejudicial error.
“To establish prejudice, [the defendant] must show a reasonable probability that but for the error the outcome of the trial would have been different.” State v. Crone, 545 N.W.2d 267, 273 (Iowa 1996); see also Tennison v. Circus Circus Enterprises, Inc., 244 F.3d 684, 688 (9th Cir.2001) (“A reviewing court should find prejudice only if it concludes that, more probably that not, the lower court’s error tainted the verdict.”). I cannot say that it is more probable than not that the bad-acts evidence introduced in this case did not affect the jury’s verdict. See Hodges, 770 F.2d at 1481. I would affirm the decision of the court of appeals, reverse the district court judgment, and remand for a new trial.
CARTER, J., joins this dissent.