(dissenting). I agree with the unanimous decision of the court of appeals that the circuit court committed prejudicial error in completely barring the defendant from cross-examining the psychiatrist-witness about a pending investigation into the witness's alleged criminal misconduct to show bias.1
*371The majority opinion holds that the test to determine whether defense counsel may cross-examine a state's witness about alleged criminal misconduct to show the witness's bias is whether a jury could find a "logical connection" between the criminal investigation of the witness and the district attorney's office on whose behalf the witness was testifying. The majority then concludes that the circuit court did not err in excluding the evidence, because "the relationship between the Dane county district attorney's office and [the witness] which would be necessary to suggest bias, interest or motive simply did not exist." Majority op. at 351.2
This test does not conform to the test set forth in earlier cases. This court and the United States Supreme Court have concluded that "a defendant, as an ingredient of meaningful cross-examination, must have the right to explore the subjective motives for the witness' testimony."3 Evidence is relevant to the issue of bias in *372this case if it tends to prove that the witness believed that he might be aided or harmed by testifying in a particular way. The focus of the circuit court's inquiry should be on the witness's state of mind.
Because I believe the majority opinion uses an incorrect standard and reaches an incorrect decision, I dissent.
H-I
I believe that the circuit court in this case had to apply the following analysis to determine the relevance of evidence proffered on cross-examination to show a witness's bias: Does the proposed cross-examination support a reasonable inference that the witness believed he might benefit if he testified in favor of the state's position, or he might be disadvantaged if he testified against the state's position?
The party asserting bias need not prove that the witness received promises from the state or would in fact benefit from or be harmed by giving certain testimony. It is enough if the witness believes he or she has a self-interest in the testimony.4
*373Even if the witness's beliefs were "absurd," the adverse party has a right and a duty to explore the witness's motives. We explained this obligation in State v. Lenarchick, 74 Wis. 2d 425, 447, 247 N.W.2d 80 (1976), as follows:
Although no promises had been made to [the witness], he may well have been testifying favorably to the state in the hope and expectation that the state would reward him by dropping or reducing pending charges. Even though that expectation were absurd, defense counsel had the right and duty to explore the witness' motives.
I conclude that the majority opinion mistakenly adopts a new test to determine the relevance of evidence to show a witness's bias that deviates from the test this court and the United States Supreme Court have established.
hH l-H
Applying the test this court and the United States Supreme Court have used to determine the relevance of evidence proffered to show bias, I conclude that the circuit court erred in barring cross-examination on the issue of bias in this case.
In reviewing the circuit court's decision about the scope of cross-examination to show bias, an appellate court must consider (1) that an adverse party is allowed great latitude regarding the subject and scope of the inquiry to show bias; (2) that the determination of the relevancy of the line of questioning proffered to establish bias is within the discretion of the circuit court;5 and (3) *374that it is error for a circuit court to bar an accused from presenting all facts from which a jury might reasonably infer bias of a prosecution witness.6
The circuit court in this case determined that the evidence proffered was "totally irrelevant and immaterial" to the issues of motive, interest or bias.7 The state argues that on a sliding scale of possible bias, the defendant's theory of bias in this case is too weak to allow the defendant to cross-examine on this subject.
Both the majority opinion and the circuit court apparently base their determination of lack of relevance on two factors and reason as follows:
1. Dr. Roberts learned two facts simultaneously. He learned that the state might investigate allegations of *375criminal conduct his patients made against him. He also learned that a special prosecutor unconnected with the Dane County district attorney's office would be in charge of the matter. Knowing that the Dane County district attorney was prosecuting the defendant in this case and another district attorney's office was in charge of a possible investigation of him for criminal charges, Dr. Roberts could not possibly think that his testimony benefit-ting the Dane County district attorney's case against the defendant could influence the outcome of his own potential criminal case.
2. Criminal charges were not filed against Dr. Roberts during the pendency of the defendant's case. Thus during the pendency of the defendant's case, because any prosecution of Dr. Roberts was "merely a possibility, there was no reasonable basis to believe that Dr. Roberts would color his report ..." or testimony. Majority op. at 352. The majority intimates that no bias can be shown unless criminal charges are filed or there is proof of actual negotiation between the witness and the state regarding specific pending charges.
This reasoning is, I believe, flawed. The majority's reliance upon the special prosecutor's being in the Milwaukee County district attorney's office and not in the Dane County district attorney’s office lends little support for the majority's conclusion. Even though the circuit court or the majority believes that the presence of two autonomous district attorney offices guarantees that the one would not influence the other, Dr. Roberts might have believed otherwise. Dr. Roberts would know that his testimony in this high profile case would be an open, public record that the special prosecutor might very well hear or read about.
The record shows that Dr. Roberts learned of his expanding difficulties with various authorities after his *376January interview with the defendant and before he filed his report in August. He learned about investigations by the University Hospital and the State Medical Examining Board and that allegations against him had been referred to the State Justice Department and the district attorney's office. Nothing in the record indicates that Dr. Roberts had formed an opinion regarding the defendant's mental state after the first interview. Indeed, Dr. Roberts interviewed the defendant in June and again in August shortly before trial in September, 1988.
A jury could infer that Dr. Roberts may have felt intensified internal pressure over the entire period to shade his testimony in favor of the state. A jury could infer that Dr. Roberts believed, however unwarranted the belief, that if he testified favorably for the state in the defendant's case, the special prosecutor might be more favorably disposed to drop the investigation; or to investigate the allegations less vigorously; or to show leniency in any charges filed or in a plea agreement or in a recommendation on sentencing.
Neither case law nor logic supports the majority's view that formal charges must be filed before an investigation into criminal behavior is relevant to the issue of bias. The cases stand for the proposition that "when a witness is subject to the coercive power of the state and can also be the object of its leniency" an adverse party must have the opportunity to explore the subjective motives for the witness's testimony. State v. Lenarchick, 74 Wis. 2d 425, 447-448, 247 N.W.2d 80 (1976).8
*377That charges had not been filed against Dr. Roberts strengthens rather than weakens the defendant's theory of bias.9 Dr. Roberts rendered his opinion on the defendant's mental capacity when he did not know what the state would do to him. The jury could reasonably infer that as long as the special prosecutor deferred action on Dr. Roberts's case, Dr. Roberts could hope — even though that hope may have been unrealistic — that he might help his own cause by testifying favorably for the state's position in the defendant's case.
In this case the range of cross-examination to show bias should be even broader than in other cases. In many areas, such as fingerprints, ballistics, and forensic chemistry, expert testimony opinions are formed from "hard" data, knowledge or principles. The opportunity for the expert opinion to be influenced by bias is limited. Psychiatry, in contrast, is a field based largely on "soft" data or knowledge. Under these circumstances the possibility increases that the psychiatrist's findings, opinions, and presentations may be slanted, consciously or unconsciously, by any biases. J. Ziskin and D. Faust, Coping *378with Psychiatric and Psychological Testimony 45 (4th ed. 1988).
I conclude that under the circumstances of this case the circuit court abused its discretion in ruling that the evidence of the criminal investigation involving Dr. Roberts was irrelevant to the defendant's theory of bias.10
HH HH
Relevant evidence, of course, may be barred if its probative value is outweighed by unfair prejudice. The circuit court may exclude relevant evidence if it has "a tendency to influence the outcome by improper means." State v. Baldwin, 101 Wis. 2d 441, 455, 304 N.W.2d 742 (1981). The state argues that unproved allegations of Dr. Roberts's sexual misconduct with patients is a "highly emotionally charged" issue that would distract the jury.
Dr. Roberts's testimony was of great importance to the state. The sole issue in the second phase of the trial was the defendant's mental state. Both the state and the defendant relied on expert witnesses to prove the defendant's mental state. Dr. Roberts was the only expert witness who saw the defendant at the critical time, the day of the offense. The jury's responsibility was to "weigh the opinion of one expert against that of another . . . considering] the relative qualifications and credibility of the expert witnesses." Wis JI — Criminal 200A *379(Rel. No. 10 — 11/83).11
The evidence of Dr. Roberts's being an object of an investigation for criminal wrongdoing was probative of bias. Any prejudice or distraction caused by giving this information to the jury could have been circumscribed by restricting the scope of the defendant's cross-examination.12 The nature of the allegations made by Dr. Roberts's patients was irrelevant to the defendant's theory of bias. The relevant information for the jury was the seriousness of the allegations, the referral of the allegations by the hospital to the state for possible criminal prosecution, and the effect on Dr. Roberts's professional career, livelihood, reputation and personal life should he be charged with or convicted of these charges.
Given an adverse party's great latitude regarding the subject and scope of an inquiry to show the witness's bias, the importance of Dr. Roberts's testimony, and the circuit court's power to curtail any undue prejudice to the state by limiting the cross-examination, the circuit court abused its discretion in barring all the proffered evidence, concluding that prejudice to the state outweighed the probative value of the evidence in this case.
IV.
I further conclude that the error barring the evidence was not harmless. Dr. Roberts was the state's primary psychiatric witness. He emphasized in his testimony the value of having interviewed the defendant on the day of the shooting — an advantage the other psychi*380atric witnesses could not claim. Despite the defendant's having the burden of proof on the mental disease or defect issue in the second half of the bifurcated trial, I conclude that prohibition of the bias evidence on cross-examination of Dr. Roberts undermines confidence in the outcome of this case. State v. Dyess, 124 Wis. 2d 525, 544-45, 370 N.W.2d 222 (1985).
V.
Finally, I register my disagreement with the majority's conclusion that the Miranda rule does not apply to Dr. Roberts's initial interview of the defendant. The United States Supreme Court has not yet decided a case which discusses the application of Miranda in situations such as the one presented in this case, namely, where the interview takes place before the accused has been charged or has raised a defense of insanity.13
The court should not reach out and decide this issue which is not presented by the facts of the case. The court of appeals correctly determined, I believe, that Dr. Roberts's Miranda warnings to the defendant were adequate and that the defendant's rights were honored. Although Dr. Roberts failed to inform the defendant that a lawyer would be provided to him at state expense, if necessary, a Dane County detective gave the defendant his full Miranda rights less than an hour before the interview with Dr. Roberts.
*381For the reasons set forth, I would affirm the decision of the court of appeals. Like the court of appeals, I would remand for a new trial on the defendant's plea of not guilty by reason of mental disease or defect.
The majority asserts that there was no evidence of any investigation of Dr. Roberts during the pendency of the defendant's case. Majority op. at 353.1 believe that for the purposes of this appeal, the fact that allegations of professional misconduct by Dr. Roberts had been referred to a special prosecutor is sufficient evidence that some kind of investigation would follow.
State v. Lenarchick, 74 Wis. 2d 425, 448, 247 N.W.2d 80 (1976) (emphasis added).
According to the United States Supreme Court, evidence relating to bias on cross-examination is relevant if a jury might reasonably find that the evidence "furnished the [state's] witness a motive for favoring the prosecution in his testimony." Delaware v. Van Arsdall, 475 U.S. 673, 679 (1986).
The circuit court must recognize that a jury need not accept the witness's denial about bias. Cross-examination should be permitted "to expose to the jury the facts from which jurors, as the *372sole triers of fact and credibility, could appropriately draw inferences relating to the reliability of the witness." Davis v. Alaska, 415 U.S. 308, 318 (1974).
In Davis v. Alaska, 415 U.S. 308 (1974), for example, the Supreme Court held that it was error to bar evidence on cross-examination that a state witness was on juvenile probation. The adverse party asserting bias in that case wished to show that the witness may have feared that his probation would be revoked and feared that he might be a suspect in the investigation. There was no suggestion that actual threats of revocation of probation had been made to the witness or that the witness was a suspect.
See also State v. Balistreri, 106 Wis. 2d 741, 753, 317 N.W.2d 493 (1982).
In Hartung v. Hartung, 102 Wis. 2d 58, 66, 306 N.W.2d 16 (1981), the court stated the method for reviewing a circuit court's discretionary determination:
*374A discretionary determination, to be sustained, must demonstrably be made and based upon the facts appearing in the record and in reliance on the appropriate and applicable law. Additionally, and most importantly, a discretionary determination must be the product of a rational mental process by which the facts of record and law relied upon are stated and are considered together for the purpose of achieving a reasoned and reasonable determination. It is recognized that a trial court in an exercise of its discretion may reasonably reach a conclusion which another judge or another court may not reach, but it must be a decision which a reasonable judge or court could arrive at by the consideration of the relevant law, the facts, and a process of logical reasoning. The record here demonstrates beyond doubt that the trial court in this case failed to articulate and use the discretionary standards which the legislature has set as guidelines for determining an award of maintenance and failed to set forth the facts upon which it relied.
State v. Lenarchick, 74 Wis. 2d 425, 446-448, 247 N.W.2d 80 (1976).
The circuit court stated: "And I think it's fair to say that, no matter what [Dr. Roberts does] for the Dane County district attorney's office, [Dr. Roberts] would not be able to influence any result, as a result of [the special prosecutor's] investigation or any judge that might ultimately hear it, should there be any charges filed."
See United States v. Garrett, 542 F.2d 23 (6th Cir. 1976), holding it was abuse of discretion for the trial court to exclude evidence that the government's witness in a drug case had been suspended from the police force because he was suspected for using hard drugs himself and had refused to submit to a urine test. The court of appeals concluded that a jury may have inferred *377that the witness looked upon a successful prosecution as a means of having his suspension lifted.
See also State v. Chesnut, 621 P.2d 1228, 1233 (Utah 1980), disapproved on other grounds, State v. Crick, 675 P.2d 527, 531 (Utah 1983) ("the mere possibility of future criminal charges is a sufficient basis to explore the motives of the witness on cross-examination [and to] place his apprehensions thereof before the jury").
The fact that the charges against Dr. Roberts were unproven might be important to the defendants' theory of admissibility based on challenging Dr. Roberts's credibility. Since I conclude that the evidence was admissible to show bias, I do not reach that issue.
Because I believe the circuit court abused its discretion in refusing to admit the evidence of bias on cross-examination, I do not reach the defendant's constitutional claim based on the confrontation clause. I note, however, that conforming to the Wisconsin Rules of Evidence may not satisfy constitutional requirements.
The members of the jury are always the "sole judges of the credibility of the witnesses and the weight and credit to be given to their testimony." Wis JI — Criminal 300 (Rel. No. 25 — 6/90).
The circuit court never considered limiting instructions, because the court ruled the evidence was not relevant.
The majority's reliance on Estelle v. Smith, 451 U.S. 454 (1981), for its conclusion that Miranda does not apply to Dr. Roberts's initial interview of the defendant is misplaced. See Comment, Fifth Amendment Limitations on the Use of Police Testimony to Rebut the Insanity Defense, 58 U. Chi. L. Rev. 359 (1991).