James and Debra Barsema (plaintiffs) petition us to review a decision of the court of appeals. We granted review to determine whether A.R.S. § 12-569 can be constitutionally applied to limit the cross-examination of an expert witness on issues pertaining to possible bias and prejudice. See Rule 23, Ariz.R.Civ.App.P., 17A A.R.S. We have jurisdiction pursuant to Ariz. Const. art. 6, § 5(3) and A.R.S. § 12-120.24.
FACTS
Plaintiffs brought a malpractice action against William Susong, M.D. (defendant). Mutual Insurance Company of Arizona (MICA) provided malpractice coverage for the claim. One of defendant’s expert witnesses was William Crisp, M.D., allegedly a MICA shareholder and insured. Dr. Crisp was a vice president and member of MICA’s board of directors. Although he was not salaried, Dr. Crisp was compensated for the duties he performed for MICA. According to Dr. Crisp, his duties as a board member included trying to keep premiums low. Basing his ruling on A.R.S. § 12-569, the trial judge granted defendant’s motion in limine to preclude plaintiffs from mentioning MICA or the fact that Dr. Crisp was involved with MICA and/or any of its committees. So far as the jury knew, Dr. Crisp was an impartial, independent expert testifying that defendant had not fallen below the applicable standard of care in treating plaintiff Debra Barsema.
The trial judge entered judgment on a verdict for defendant and plaintiffs appealed. The court of appeals held A.R.S. § 12-569 unconstitutional
1
and found the trial judge erred in prohibiting plaintiffs from cross-examining Dr. Crisp regarding his employment relationship with MICA.
Barsema v. Susong,
THE STATUTE
1. Scope
The relevant portions of § 12-569 provide:
During the trial of a medical malpractice action ... evidence that ... any witness ... has been or is covered by a professional liability insurance policy issued by a health care insurer established pursuant to [A.R.S. §§ 20-1721 to -1724] or that such ... witness has a financial interest in the operation of such a health care insurer arising as a result of the ownership of stock, a policy or policies of insurance, notes, including contributed surplus notes, any other evidence of in *312 debtedness, or otherwise, shall not be received in evidence for any purpose.
(Emphasis added.)
In holding that the trial court erred, the court of appeals found “[ejvidence of Dr. Crisp’s bias, interest, and agency would clearly have been admissible under Rule 411,” Ariz.R.Evid., 17A A.R.S.
2
Op. at 307,
In oral argument before this court, defendant all but conceded that the statute would be unconstitutional if interpreted to forbid the admission of Dr. Crisp’s employment relationship with MICA. Were such a prohibition explicit in the statute, we would not hesitate to agree with the court of appeals that it was facially invalid for the reasons set forth in that court’s opinion. Defendant now argues that it is not necessary to interpret § 12-569 so broadly. The statute does not by its terms forbid cross-examination of a defense expert in order to establish that he is an officer, director or employee of the insurance carrier that indemnifies the defendant for the loss arising from the subject of the litigation. Defendant’s concern, instead, turns to the admissibility of evidence that the witness and the party share a common insurer.
2. Correlation of A.R.S. § 12-569 and Rule 411
The court of appeals did not consider the statute’s constitutionality if given a limited construction, as defendant now urges it should be, so that it forbids only an attempt by plaintiffs to establish that Dr. Crisp was covered by the same insurance carrier as defendant. Defendant contends that the statute may be upheld insofar as it forbids evidence that a defense expert might be biased simply because he or she was insured by the same company as defendant. Because MICA was organized in response to the alleged malpractice crisis in 1974-75 4 many Arizona doctors are insured by it. Defendant fears, therefore, that absent A.R.S. § 12-569, 5 plaintiffs’ counsel could often interject the issue of insurance when cross-examining defense experts who had the same insurance carrier as defendant. This could be done on the theory that the expert was biased because any verdict against defendant might affect insurance premiums charged Arizona doctors, including the particular witness. We do not believe defendant’s fears are well founded.
The interjection of insurance is prejudicial in negligence cases primarily because it may affect the findings of some jurors on the questions of liability and damages, when it is not relevant to either.
Muehlebach v. Mercer Mortuary & Chapel,
These common law principles have been codified in Rule 411:
Evidence that a person was or was not insured against liability is not admissible upon the issue whether he 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.
(Emphasis added.) Rule 411 appears in that section of the rules dealing with evidence that shares the common attribute of ordinarily having little or no relevancy but substantial capacity for creating prejudice. This section includes subsequent remedial measures, offers of compromise, defendant’s offers to pay expenses caused by his conduct, and offers to plead guilty.
See
Rules 407 through 410. However, these rules all share the common exception that allows admission of such “dangerous” evidence when offered for a purpose other than the least relevant and most prejudicial purpose: that of affecting the jury’s findings on liability and damages.
See, e.g., Readenour v. Marion Power Shovel,
Even when the evidence has a relevant purpose, the rules provide fürther protection from prejudice. Evidence relevant to one issue, such as bias, but prejudicial to another, may be admitted only if it passes the “threshold of Rule 403, which permits the
trial judge
to exclude relevant evidence where the probative value is ‘substantially outweighed’ by any of a variety of factors, including ‘danger of unfair prejudice.’ ”
Id.
at 449,
3. Application to Cases Where Defendant and Witness Have a Common Insurer
Given the currently raging debate over the relationship between malpractice cases and malpractice insurance, we think it certain that in every jury there will be at least one member who has heard of malpractice insurance. See M. UDALL & J. LIVERMORE, ARIZONA PRACTICE: LAW OF EVIDENCE § 91 (2d ed. 1982). But even acknowledging that most jurors may surmise that defendant is insured, the introduction of evidence on the subject tends to emphasize something that is usually irrelevant and that may have an adverse effect on the quality of the jury’s deliberations and conclusions. As noted in the previous section, the Rules of Evidence are adequate in addressing this problem. Therefore, we do not accept defendant’s implicit hypothesis that absent A.R.S. § 12-569 plaintiffs would always be free to show bias by cross-examining a defense expert to prove that he and defendant had the same insurer. In most cases, the conclusion that a witness would be biased because he or she and a party had the same insurer is so attenuated that the predicate evidence — proof of insurance — is of questionable relevancy, even if it could be established as a fact. See Rule 401.
Of course, we acknowledge that in dealing with a captive insurer such as MICA, with a comparatively small premium pool, evidence of a common insurer between the witness and the defendant might be more relevant than in ordinary cases. Nonetheless, we believe defendant’s apprehensions are unsupported. In all but the exceptional case, a trial judge applying Rule 403 should hold that the danger of prejudice resulting from the interjection of insurance evidence substantially outweighs the probative value of evidence that the witness and a party have a common insurer. In all but exceptional cases, therefore, the type of evidence that concerns defendant would not be admitted if the trial court follows the process contemplated when Rules 411, 401 and 403 are invoked.
*314
This brings us to the portion of the statute prohibiting proof that “any witness ... has been or is covered by a professional liability insurance policy” issued by MICA. As we indicated in
Readenour,
our constitutional rulemaking power is based upon art. 6, § 5 of the Arizona Constitution and the separation of powers doctrine contained in art. 3.
We do not believe A.R.S. § 12-569 merely supplements the rules so that we could defer to the legislature to promote a substantive goal of public policy.
Cf. Readenour,
Under the state constitution, wé can neither allow the legislature to define what is relevant,
Readenour,
nor allow it to substitute a different analytical framework or make special rules for a particular case, setting aside those evidentiary rules which over the centuries have been found necessary to ensure fair trials.
See State v. Robinson,
Thus, we conclude that under the Rules of Evidence the trial judge properly could have excluded evidence that Dr. Crisp was insured by MICA, but erred in precluding the introduction of evidence that Dr. Crisp was MICA’s vice president and a member of its board of directors.
HARMLESS ERROR
We turn then to determine whether the error requires reversal. The court of appeals noted that several doctors testified for defendant on the issue of negligence. Without reviewing a transcript, it could not determine whether the improper restriction of Dr. Crisp’s cross-examination had prejudiced plaintiffs. Plaintiffs, the appellants in this case, bear the burden of proving that the trial court’s decision, even if incorrect, was prejudicial. 156 Ariz. at —-,
A decision involving the admission or exclusion of evidence, if erroneous, will not warrant reversal unless it affects a substantial right of the parties.
State ex rel.
*315
LaSota v. Arizona Licensed Beverage Association,
The opinion of the court of appeals is approved, as supplemented by this opinion. The judgment is affirmed.
Notes
. In his motion in limine, defendant moved to exclude evidence that Dr. Crisp was either insured by or had an employment relationship with MICA, claiming the statute prohibited examination "for any purpose.” Presumably, the trial judge granted the motion on those grounds, no others having been raised to him or mentioned by him. Plaintiffs did not object to the exclusion on constitutional grounds; however, they did raise the issue in their motion for new trial. Ordinarily, an appellate court will not consider an issue first raised on appeal.
Dombey
v.
Phoenix Newspapers, Inc.,
. Arizona Rules of Evidence will hereafter be referred to as Rule-.
. The court also relied on our holding in
Jones v. Munn,
. Medical Malpractice Act of 1976, ch. 1 (1st Spec.Sess.), 1976 Ariz.Laws 989;
see also Eastin v. Broomfield,
. A.R.S. § 12-569 was part of the Medical Malpractice Act of 1976.
