Opinion of the Court by Justice ROACH.

I. INTRODUCTION

This is an appeal of a jury verdict in a personal injury action that was brought by Appellant, Amanda Baker, against Appellee, Theresa Kammerer. At trial, Baker was not permitted to cross-examine Hope Frost, an investigator employed by Kammerer's insurance carrier, about possible bias stemming from her employment. The Court of Appeals affirmed the trial court. Because we hold that the trial court abused its discretion in limiting the cross-examination of Frost, we hereby reverse.

II. BACKGROUND

This case involves a personal injury claim arising from an accident in which Baker, who was crossing the street on foot, was struck by an automobile driven by Kammerer. Baker sought various damages, including medical expenses of over $5,000.00. At trial, the parties contested the circumstances of the accident, particularly whether Baker was inside the designated crosswalk when she was hit and whether the traffic signal favored Kammerer.

Prior to opening statements, Kammerer's counsel indicated to the trial court that he had received supplemental discovery information shortly before trial suggesting that Baker intended to call two eyewitnesses, Aleisha Sams and Leah Edmonds, to testify on her behalf. He stated, "One of those witnesses spoke to Hope Frost, who's in the courtroom right now, and gave a statement. If she testifies inconsistently with that statement, I might call Hope Frost." As noted above, Frost was an investigator employed by Kammerer's insurance provider. Baker's attorney asserted that if Frost testified he was "going to have to identify who Hope [Frost] is — she's the insurance adjuster." While counsel continued to discuss the point, the judge noted, "My suggestion is, you don't have to identify [Frost], she's just a person the witness spoke to."

Later in the trial, after both Sams and Edmonds had testified on behalf of Baker, Kammerer asked to call Frost for the limited purpose of rebutting the testimony of the two witnesses. According to Kammerer, both Sams and Edmonds had testified inconsistently with statements they had previously made to Frost. Baker's counsel objected on the grounds that Frost had not been listed as a witness in any of the pretrial discovery materials submitted by Kammerer as required by CR 93.04. Kammerer's counsel responded that he had not disclosed Frost as a potential witness because he had not planned to call her until the alleged inconsistencies in the testimony of Sams and Edmonds surfaced at trial.

The trial court held a discussion in chambers to address the merits of Baker's objection and to decide whether Frost would be allowed to testify. During that discussion, Baker's counsel argued that Frost should not be allowed to testify because she had not been identified by Kammerer prior to trial. Baker's counsel also argued that if Frost was allowed to testify, he should be allowed to ask her questions about the nature of her involvement in the case, specifically her employment by Kammerer's insurer.

Kammerer's attorney countered that prior to hearing the testimony of Edmonds and Sams, he had no reason to believe Frost's testimony would be necessary. He further stated that inadequate discovery responses by opposing counsel had prevented him from contacting and interviewing witnesses, making inconsistencies in their testimony undiscoverable. Following this exchange, the trial court ruled that Frost would be allowed to testify, stating, "I'll allow her to testify, I think that forms a sufficient basis in the record."

The judge went on to advise counsel for both sides that no mention was to be made of Frost's employment by Kammerer's insurance company. Although Baker's attorney had specifically raised this issue, arguing that Frost's cross-examination would necessarily involve questions regarding her employment, Kammerer's attorney did not even address this argument, concentrating instead on his primary request that Frost be allowed to testify. Nevertheless, the judge stated unequivocally, "And contrary to what counsel says, it will be a mistrial if you [disclose Frost's employer]. You just say, you can state the term `investigator,' that's all that needs to be said. You don't have to go into anything else — investigator."

After this statement, Baker's attorney interrupted the judge in an attempt to explain the discovery violation that had been alleged by opposing counsel. The judge responded:

I'm telling you why I'm making the ruling that I am. Had you spelled out in detail what they were going to say, I wouldn't be ruling this way, believe me. If you had spelled out in your exchange what they would have been saying — but because you didn't and because of the fact that these aren't anybody's witnesses as such, they don't belong to anybody. So, based upon that fact, I think clearly counsel has the opportunity, especially in light of the fact . . . of the representation of inconsistent statements.

(Emphasis added.) Although his remarks are somewhat ambiguous, when considered in context, the judge's explanation seems to be offered as a rationale for his primary ruling that Frost would be allowed to testify. In particular, the trial court's statement, highlighted above, that "clearly counsel has the opportunity" seems to refer specifically to that aspect of the dispute. After this statement, the parties returned to the courtroom and the trial resumed. Shortly thereafter, Frost testified regarding her previous meetings with Edmonds and Sams. As directed by the judge, neither party made any mention of Frost's employer, nor did they attempt to explain her role in the case. After Frost's testimony the defense rested.

Shortly after the jury began deliberating, they submitted two questions to the trial court. Those questions were "Who is Hope Frost?" and "What's her interest in this case?" The trial court informed the jury that it could not answer either of the questions. The jury continued its deliberations and ultimately returned a verdict for Kammerer. Baker filed a motion for a new trial, which was denied.

Baker then appealed to the Court of Appeals and specifically objected to the testimony of Hope Frost. Despite her claims of error, the Court of Appeals affirmed the judgment of the trial court, holding that it was not error to admit the testimony of Frost and that it was not an abuse of discretion to refuse requests by Baker's attorneys to be able to cross-examine Frost regarding potential bias stemming from her employment. We subsequently granted Baker's motion for discretionary review.

III. ANALYSIS

In deciding Baker's direct appeal, the Court of Appeals addressed two alternate claims of error: (1) that the testimony of Hope Frost should not have been admitted, and (2) that Baker's attorney should have been permitted to cross-examine Frost regarding her employment as a means of showing her alleged bias. On this appeal, Baker has elected to pursue only the second claimed error.

At the outset we acknowledge the general rule that "`[t]he presentation of evidence as well as the scope and duration of cross-examination rests in the sound discretion of the trial judge. This broad rule applies to both criminal and civil cases. . . .'" Commonwealth v. Maddox, 955 S.W.2d 718, 721 (Ky. 1997) (quoting Moore v. Commonwealth, 771 S.W.2d 34, 38 (Ky. 1988)); see also Com., Dep't of Highways v. Smith, 390 S.W.2d 194 (Ky. 1965) ("[T]he trial court is vested with a sound judicial discretion as to the scope and duration of cross-examination. Were this not so, any trial could be rendered a farce and mockery; witnesses could be insulted and threatened; juries would become exhausted and exasperated; justice could be frustrated and thwarted."). But we also note that:

Opportunity for cross-examination of witnesses is seen as indispensable to the search for truth in litigation. . . . The Evidence Rules say nothing about a "right" to cross-examination, perhaps because nothing needs to be said about a practice so fundamental to the litigation process. KRE 611(b) addresses the subject of "scope of cross-examination" but undoubtedly contemplates that litigants will be given an opportunity to subject evidence to the cleansing and clarifying process of cross examination.

Robert G. Lawson, The Kentucky Evidence Law Handbook § 3.20[3], at 239 (4th ed. 2003) [hereinafter Lawson, Kentucky Evidence].

Likewise, we have held that "[t]he credibility of a witness' relevant testimony is always at issue and the trial court may not exclude evidence that impeaches credibility even though such testimony would be inadmissible to prove a substantive issue in the case." Sanborn v. Commonwealth, 754 S.W.2d 534, 545 (Ky. 1988). "A wide array of evidence is admissible only because it renders testimonial credibility more probable or less probable than it would be without the evidence." Lawson, Kentucky Evidence § 5.05[3], at 82. This language illustrates one of the most crucial goals of cross-examination, namely, exposing the bias of an opposing witness. Ultimately, the law favors admissibility of evidence of bias.

Though decided prior to our adoption of the rules of evidence, our predecessor court traditionally allowed the introduction of insurance evidence to show the bias of a witness. See, e.g., Nunnellee v. Nunnellee, 415 S.W.2d 114, 116 (Ky. 1967) ("We have held that it is proper to show, as here, that a witness represents an insurance company in order to disclose his possible bias."). The admissibility of evidence of insurance coverage would seem to have been complicated by the enactment of KRE 411, which prohibits the admissibility of evidence of a defendant's liability insurance to prove negligence or fault. However, the rule provides certain exceptions to this prohibition, in essence, retaining those recognized at common law. The rule states:

Evidence that a person was or was not insured against liability is not admissible upon the issue whether the person acted negligently or otherwise wrongfully. This rule does not require the exclusion of evidence of insurance against liability when offered for another purpose, such as proof of agency, ownership, or control, or bias or prejudice of a witness.

KRE 411 (emphasis added).

While a decision as to the admissibility of such evidence still rests within the discretion of the trial judge, that discretion is not limitless. The law favors the admission of evidence that is relevant to a jury's determination of a witness's credibility. As with most evidentiary decisions, the trial court's discretion in this area stems from its gatekeeping function under KRE 403. As noted by Professor Lawson, "protection against excessive use of the `other purposes' clause of Rule 411 is provided by Rule 403, which requires a balancing of probative value against undue prejudice." Lawson, Kentucky Evidence, § 2.60[3], at 210. This approach was specifically adopted in Wallace v. Leedhanachoke, 949 S.W.2d 624 (Ky.App. 1997), where the Court of Appeals held that the trial court had not abused its discretion in prohibiting the introduction of KRE 411 "other purposes" evidence which alleged bias of an expert witness due to the commonality of insurance carriers between a physician defendant and the expert. In affirming the decision to exclude the evidence, the Court of Appeals noted, "we adopt the balancing test [of KRE 403] to allow trial courts to exercise their broad discretion on a case-by-case basis." Id. at 628.

In this case, the identity of Hope Frost's employer went to the heart of her potential bias and would likely have been crucial to the jury's assessment of her credibility. It is clear from their questions to the judge that Frost's identity was particularly important to the jurors who decided the case. Having been presented evidence that the incident had been investigated by police, the jurors were forced to consider Frost's testimony, without any explanation of her involvement in the case or her role as an "investigator." And it is possible, perhaps even likely, that the trial court's instruction to use the term "investigator" to describe Frost not only prevented the jury from knowing the truth but may actually have misled it about Frost's interest in the case.

Given the fundamental importance of the ability to cross-examine as to bias and the trial court's apparent failure to engage in any meaningful analysis under Rule 403 before prohibiting cross-examination as to Frost's employment, we conclude that the trial court abused its discretion in this case. In reaching this conclusion, however, we must also note that we are not mandating the disclosure of evidence relating to insurance in every case like the one before us. To the contrary, our holding still recognizes the trial court's inherent discretion over evidentiary questions such as this one. Because a multitude of factors may be considered by a trial judge addressing such an issue, judges are free to consider a spectrum of potential remedies. In an appropriate case, a judge might reasonably conclude that insurance evidence should be freely admitted. Another judge might choose a middle ground, allowing the identification of a witness as an agent of the defendant, but refusing to allow the disclosure that a defendant is insured. Likewise, applying the balancing test of KRE 403 might lead to the conclusion that certain insurance evidence is inadmissible. See, e.g., Wallace, 949 S.W.2d at 628.

That being said, it is hard to imagine any case involving circumstances similar to these in which a trial court decision that completely shields the jury from evidence of possible bias would not be an abuse of discretion. As noted above, dual concerns — the general inclusionary thrust of the Rules of Evidence and the more particular preference to allow evidence of bias — weigh heavily in favor of admissibility. Absent unusual circumstances wherein the evidence would be either extremely prejudicial or minimally probative, the principal question is the scope of the evidence of bias to be allowed. As with the broader question of initial admissibility, the balancing test of KRE 403 provides a useful tool for determining the scope of the evidence to be admitted. Therefore, on retrial, the trial court shall be guided by KRE 403 to determine whether Frost shall be identified as an agent of Defendant, an employee of the insurance carrier, or otherwise.

Kammerer argues that the trial court properly exercised its discretion in limiting the scope of Frost's cross-examination, contending that the court's ruling operated as a quasi-sanction for Baker's alleged discovery violation. Having reviewed the record, however, it seems more likely that the trial court's reference to discovery deficiencies was offered as justification for its ruling on the ultimate question of whether Frost would be allowed to testify — not to the more limited question as to the scope of her cross-examination. Even if Kammerer is correct, however, such a violation is not a proper basis for limiting the scope of cross-examination to exclude evidence of possible bias because a discovery violation has little significance to the factors to be considered under the KRE 403 balancing test.

A trial judge may always exclude evidence when its probative value is substantially outweighed by its risk of undue prejudice. Normally, we would even assume that admitted evidence has been subjected to this balancing test. However, the record in this case suggests the trial court did not engage in the KRE 403 analysis. When the possibility that Frost might be called as a witness was first raised, the judge clearly signaled his intention to exclude any mention of Frost's role as an insurance agent by stating, "you don't have to identify [Frost], she's just a person the witness spoke to." Such a statement suggests the trial court employed a rigid, per se exclusion of any evidence of insurance as opposed to the flexible, case-by-case approach required by KRE 403 once one of the "other purposes" exceptions of KRE 411 is met.

IV. CONCLUSION

The trial court's refusal to allow Baker to cross-examine Frost as to her possible bias was an abuse of discretion and is sufficient to warrant a new trial. Accordingly, the judgment of the Court of Appeals is reversed and the case is remanded to the Campbell Circuit Court for further proceedings consistent with this opinion.

LAMBERT, C.J.; GRAVES, and JOHNSTONE, JJ., concur.

COOPER, J., dissents by separate opinion in which SCOTT and WINTERSHEIMER, JJ., join.