(dissenting):
The decisive issue in this tragic case is whether the trial court erred when, over objection, it permitted the prosecutor to cross-examine two professionals who were called by the defendant as expert witnesses in support of his mental illness defense.1 Because I believe the trial court’s ruling was well within the perimeter of the discretion the law affords to trial judges in this area, I respectfully dissent both from the majority’s conclusion that the prosecutor’s cross-examination was improper or prejudicial, and from its remand for a new trial of the mental illness defense.
*544A witness qualified as an expert by knowledge, skill, experience, training, or education is permitted to testify and give professional opinions on crucial issues in criminal as well as in civil cases if the testimony will aid the jury in resolving the issue. Minn.R.Evid. 702. Concomitant with qualifying the witness as an expert, the party calling the witness frequently tries to augment his or her credibility by, in addition, eliciting from the witness “facts” designed to create an impression of disinterest and impartiality. In the instant case appellant’s counsel followed that general practice. On direct examination he educed from Dr. Stephans that he had evaluated several scores of persons in criminal matters, had testified in a number of criminal cases, and had been retained by the state to render services in unrelated civil matters. The result of this line of questioning was to clothe Dr. Stephans with an aura of impartiality. It suggested that he was a detached, disinterested, scientific professional without any proclivity to favor an accused in a criminal case who seeks to escape retribution by advancing a mental illness defense. I do not suggest that by so doing counsel did anything wrong or even unusual. Perhaps, in fact, Dr. Stephans possessed those characteristics when he assumed the witness stand. Nevertheless, the prosecutor had the right to attempt to place that alleged impartiality in proper perspective, by cross-examination which revealed that Dr. Stephan and Dr. Perkins, a psychologist who also testified, had worked together “on recent major criminal cases,” had always testified for the defense in criminal cases in recent years, and, further, had testified, in particular, in the notorious criminal cases referred to in footnote 1 of the majority opinion. The ruling of the trial judge in denying the objection of appellant’s counsel to the latter line of cross-examination and the trial court’s subsequent denial of a mistrial motion raise the issues that are before us on this appeal.
The law has long recognized the propriety of a litigant’s attempt to elicit facts through cross-examination justifying an inference of partiality or bias of the witness. See, e.g., McCormick on Evidence, ch. 5, § 40 (E. Cleary 3d ed. 1984). The majority acknowledges the utility of the rule which permits a wide latitude of cross-examination designed to uncover information to aid the finder of fact in assessing the extent of any bias the witness may have as bearing on credibility. The majority acknowledges that courts therefore place few restraints upon the scope of permissible cross-examination for that purpose. However, it seems to me that the majority would confine that otherwise salutory and generally unlimited right to cross-examination for bias or partiality to civil litigation, but in criminal cases would unduly circumscribe its scope by reference to precatory language in the ABA Standards exhorting prosecutors to “seek justice.” Few would quarrel with that amorphous aphorism. Nonetheless its recitation, in my view, provides very little objective guidance to defining the limits of prosecutorial conduct in cross-examining for credibility.2
In my view the prosecutor’s duty is fulfilled when the prosecutor has, consistent with established rules of law, offered to present all relevant evidence bearing on culpability, or the lack thereof, to aid the jury in resolving the case, including information relative to the credibility of witnesses. The law wisely places in the trial judge the discretion to delineate the boundaries of the inquiry, and it is for the trial judge to determine whether “unfair prejudice” will result from the inquiry. The individual judge has some latitude in drawing the line beyond which cross-examination may not go in light of the circumstances inherent in the “setting” of the particular trial. Even so, that discretion itself is limited by the precept that undue restriction of cross-examination impinges upon a substantial right and by the law’s safeguard that trials *545should be fair. See, e.g., State v. Elijah, 206 Minn. 619, 625, 289 N.W. 575, 579 (1940). We should not ignore the fact that the law is concerned that in a criminal trial the state, as well as the accused, not be deprived of a fair trial. See Minn.R. Crim.P. 1.02.3
Since the earliest days of statehood, this court has consistently held in both criminal and civil cases that bias, state of mind, and inclinations of witnesses, upon whose testimony in part the issue is to be determined, are not collateral or immaterial matters; that cross-examination on the issue of bias or interest is a matter of right; and that its denial or undue circumscription is prejudicial error. See, e.g., State v. Dee, 14 Minn. 35, 37 (Gil. 27, 30) (1869); Alward v. Oakes, 63 Minn. 190, 193, 65 N.W. 270, 271 (1895); Elijah, 206 Minn, at 625, 289 N.W. at 579. In the latter case we quoted with approval the observation of the Supreme Court of the United States in Alford v. United States, 282 U.S. 687, 692, 51 S.Ct. 218, 219, 75 L.Ed. 624 (1931),
Prejudice ensues from a denial of the opportunity to place the witness in his proper setting and put the weight of his testimony and his credibility to a test, without which the jury cannot fairly appraise them. * * * To say that prejudice can be established only by showing that the cross-examination, if pursued, would necessarily have brought out facts tending to discredit the testimony in chief, is to deny a substantial right and withdraw one of the safeguards essential to a fair trial.
Elijah, 206 Minn. at 625, 289 N.W. at 579.
Rule 402, Minn.R.Evid., which provides that relevant evidence is admissible at trial, is identical to its federal counterpart, Fed. R.Evid. 402. Under either, credibility evidence is almost always relevant. “Proof of bias is almost always relevant because the jury, as finder of fact and weigher of credibility, has historically been entitled to assess all evidence which might bear on the accuracy and truth of a witness’ testimony.” United States v. Abel, 469 U.S. 45, 52, 105 S.Ct. 465, 469, 83 L.Ed.2d 450 (1984). Although Rule 403, Minn.R.Evid., excludes relevant evidence if its “probative value is substantially outweighed by the danger of unfair prejudice,” nonetheless, the Alford rule implicitly circumscribes the discretion of trial courts to limit cross-examination for bias. Elijah, 206 Minn. at 625, 289 N.W. at 579.
By cross-examination of these two witnesses, particularly Dr. Stephans, the prosecutor was attempting to dispel the aura of impartiality that lingered after defense counsel had completed his direct examination. His purpose, obviously, was to attempt to elicit facts which might cause the jury to assess the objectivity of those two witnesses with some scepticism. Its probative value was very high. See, e.g., State v. Larson, 369 N.W.2d 561, 565 (Minn.App.1985), rev’d on other grounds, 389 N.W.2d 872 (Minn.1986). That these experts for several years prior to this trial had testified with respect to mental illness defenses only on behalf of the accused in criminal trials, and had done so in certain notorious cases, were relevant facts for jury consideration in assessing weight to be given to the testimony of the experts in this case. A different trial judge might have exercised his or her discretion to circumscribe the scope of the prosecutor’s cross-examination. Had that occurred, I would be inclined to affirm that decision. However, because this evidentiary ruling fell within the realm of the judge’s judicial discretion, I am unwilling to hold as a matter of law that his refusal to curtail the prosecutor’s *546cross-examination was an abuse of that discretion. By attempting on direct examination to cloak these experts with the mantle of impartiality, defense counsel “opened the door” to prosecutorial inquiry as to the nature and extent of the suggested objectivity. Having presided over both phases of the trial, the judge was in a better position than we on an appellate court to appreciate the import of the extensive evidence that would at least support, if not compel, a lay conclusion that whatever appellant’s mental state on the fateful day, it was not of the type to satisfy the statute’s “right-wrong” test. Moreover, the judge undoubtedly recognized and appreciated the favor with which the law looks upon cross-examination as to bias and credibility, and, accordingly, the effect that has on a court’s discretion to circumscribe its scope.
The majority opinion implicitly concedes the relevancy of the evidence sought by the cross-examination. It argues, however, that it was only cumulative, at best, and was otherwise “highly prejudicial.”4
Certainly no grounds for a new trial exist because the trial court declined to circumscribe an inquiry into evidence that was merely cumulative. Under Rule 403, Minn.R.Evid., the only ground of exclusion applicable here is that the evidence’s probative value is “substantially outweighed” by the danger of “unfair prejudice.” For relevant evidence to be eligible for exclusion under Rule 403, Minn.R.Evid., the danger of unfair prejudice, or the needless presentation of cumulative evidence, must substantially outweigh its probative value. In the light of the extensive latitude the law affords to a party’s right to cross-examine as to credibility, I cannot conclude that the trial court erred in failing to cut short the prosecutor’s cross-examination on this issue and, most certainly, in my opinion, not so much as to justify the grant of a new trial. Apparently, even appellant’s trial counsel did not consider the prosecution’s cross-examination to be “unfairly prejudicial;” his only objection was on the ground of relevancy.
Moreover, even absent the prosecutor’s cross-examination of these two witnesses, the trial record is replete with evidence to sustain the jury’s verdict. Thus, even could I concede that the trial court abused its discretion in refusing to curtail the cross-examination, I would hold such error, at most, was harmless beyond a reasonable doubt. The defendant’s own testimony, and the subjective and objective medical findings of examining physicians as well as those of the state hospital personnel indicate that, although appellant had undoubtedly suffered from depression following his stroke during surgery, his memory function was unusual for a stroke victim, and there existed no indication of disfunction in the limbic system (which, when damaged, may result in violent and uncontrollable rage reactions). Also, the evidence before the jury showed without dispute that appellant deliberately loaded into his Luger pistol a full ammunition clip, pocketed a second full clip, and went out to confront his estranged wife and a niece with whom she was staying. Moreover, the evidence demonstrated he knew that he had a lethal weapon, that it was criminal or wrong to shoot a human being with it, and that anyone who did so should be punished. Notwithstanding that understanding, he did empty the loaded gun clip of the Luger, fatally wounding his wife and seriously injuring two others before being subdued. In view of that overwhelming evidence, I cannot conclude other than that if the trial court committed error, the error was harmless beyond any reasonable doubt.
The jury heard all the evidence in both phases of the trial. It was fully apprised of the changes in appellant’s mental and physical conduct following the stroke. No dispute exists that at the time of the tragic *547incident the appellant suffered a mental illness known as depression.5 Yet, being privy to all that, the jury after being properly instructed on the law of the mental illness defense rejected appellant’s claim. While it may be difficult for us to fathom their rejection of that defense, it just may be that they followed their jurors’ oath and determined that at the time of the offense the appellant, notwithstanding his depression, did appreciate the nature of his act and that it was wrong. See State v. Bott, 310 Minn. 331, 333-34, 246 N.W.2d 48, 51 (1976).
No one who reads this record of a family tragedy can help but empathize not only with appellant but also with the entire family. While appellant’s mental illness in one sense may have been, and most likely was, a causative factor in these events, he failed to establish what the law requires by a greater weight of the evidence — that he did not know the danger of his act or that it was wrong.
Because I conclude the trial court did not abuse its discretion in ruling on the prosecutor’s cross-examination; because that cross-examination was directed toward delving into relative and probative evidence as to bias or partiality of the witnesses on a subject which had been opened up by the defense; and because even if the trial court did err in permitting the cross-examination, the error, in my view, was harmless, I would affirm.
. The mental illness defense was asserted in the second part of the trial which had been bifurcated as provided in Minn.R.Crim.P. 20.02, subd. 6(2). The mental illness defense is based on Minn.Stat. § 611.026 (1988), which, in essence, restates the M’Naghten "right-wrong” test and reads:
611.026. Criminal responsibility of mentally ill or deficient.
No person shall be tried, sentenced, or punished for any crime while mentally ill or mentally deficient so as to be incapable of understanding the proceedings or making a defense; but the person shall not be excused from criminal liability except upon proof that at the time of committing the alleged criminal act the person was laboring under such a defect of reason, from one of these causes, as not to know the nature of the act, or that it was wrong.
See M’Naghten's Case, 10 Cl. & F. 200, 8 Eng. Rep. 718 (H.L.1843) (opinion of Lord Chief Justice Tindal).
. As intriguing as a peregrination through the centuries to examine the reflections of philosophers from before the time of Aristotle to modern times on the meaning of the word “justice” might be, it would, of course, be inappropriate here. In passing, however, it might not be inappropriate to note that, like beauty, "justice" is often perceived from the standpoint of the beholder.
. Other legal rules condone or authorize the introduction of relevant evidence against the accused although it can be argued that its admission creates a danger of unfair prejudice far outweighing its probative value. For example, if an accused testifies, he may be impeached by his prior felony record. Minn.R.Evid. 609(a). This is permitted, though undoubtedly often highly prejudicial to an accused charged with a specific current crime, so that the jury will have the "whole picture,” and not a one-sided view of the accused. Likewise, under certain circumstances and for certain purposes, the law permits the state to introduce evidence of other crimes — evidence which may be extremely prejudicial — so that the state, as well as the accused, gets a fair trial. See, e.g., Minn.R.Evid. 404(b); State v. Spreigl, 272 Minn. 488, 491, 139 N.W.2d 167, 169 (1965); State v. Billstrom, 276 Minn. 174, 176-77, 149 N.W.2d 281, 283 (1967).
. I note the only objection raised by defense counsel at trial to the prosecutor’s cross-examination of Dr. Stephans was that the information sought was "irrelevant.” The record shows no claim that the evidence sought was unfairly prejudicial, nor did defense counsel impose a similar objection to the prosecutor’s final argument, or seek any cautionary instruction. See State v. Ture, 353 N.W.2d 502, 516 (Minn.1984) (normally, a defendant’s failure to object to improper statements made during final argument forfeits the right to consider the impropriety on appeal).
. At the time of the appeal appellant was being treated for his mental illness at the Moose Lake State Hospital.