*520Opinion
WIENER, J.Raymond Hayes appeals after a jury convicted him of premeditated first degree murder (Pen. Code, §§ 187, 189) with a firearm use enhancement (§ 12022.5) and the trial court denied his motion for a new trial. Because we conclude the new trial motion should have been granted, we reverse.
Factual and Procedural Background
On July 24, 1983, a black Ford Thunderbird registered to Hayes stopped near the corner of Oceanview and Milbrae Streets in San Diego. Hayes, who was a passenger in the car, called out to several people standing nearby and requested a PCP cigarette which he referred to as a “life” or a “sherm stick.” Several people approached the car including the eventual victim, sixteen-year-old Terry Clemons. Clemons showed Hayes two “sherm sticks.” Hayes took one and gave Clemons a rolled up piece of paper. When Clemons discovered that the piece of paper was not a $10 bill, he returned to the car window and demanded his money. Hayes then pulled a gun and shot him. Clemons later died of a gunshot wound to the head.
At trial, four eyewitnesses testified in varying detail as to the events surrounding the shooting. In addition, the People elicited testimony indicating that approximately a week and one-half before Terry Clemons was shot, Hayes had obtained a “sherm stick” from another PCP dealer near the corner of Oceanview and Milbrae, and had attempted to drive away without paying for it. In response, the dealer ran after Hayes and stabbed him in the neck with a knife. The People theorized that on the night in question, Hayes had returned to the same area with the idea of ripping off another PCP dealer and shooting him if there was any trouble.
Hayes did not testify. The only defense witness was Dr. Mark Kalish, a psychiatrist specializing in drug-related problems. On voir dire prior to his testimony before the jury, Dr. Kalish testified as to his clinical opinion that Hayes was under the influence of PCP at the time of the shooting. This opinion was based on a variety of factors, including: a blood test performed on Hayes approximately 18 hours after the shooting which revealed evidence of PCP, Seconal and a derivative of Valium; Hayes’ history of drug abuse for pain killing purposes, related to a firearm accident as a child which left him partially paralyzed; police reports recounting Hayes’ statements to officers at the time of his arrest; and Kalish’s personal examination and interview of Hayes. Defense counsel proposed to ask Dr. Kalish a hypothetical question that assuming Hayes was under the influence of PCP at the time of the shooting, did the doctor have an opinion as to Hayes’ *521ability to entertain the requisite mental state for premeditated first degree murder?1 The prosecutor argued that such opinion testimony was inadmissible because there was no foundational evidence before the jury indicating that Hayes was under the influence of PCP at the time of the shooting: “There has to be evidence in the trial, not in inadmissible material which is not before the jury. The fact is that during this trial there is no evidence upon which to base such a hypothetical. ”
The trial court eventually agreed with the prosecutor, concluding there was no evidentiary basis for Dr. Kalish’s opinion. Defense counsel then asked the court if its ruling would be different “if, in fact, there was some evidence before the court . . . that [Hayes] was under the influence of PCP at the time?” The court replied: “If there was some evidence that he was under the influence at the time of the shooting, then I think the doctor’s opinion would be admissible, that would be that at that time—I would assume his testimony is at the time of the shooting he actually was unable to form this malice aforethought because he was under the influence of PCP. If that were to be the opinion and there was some testimony that would support a finding that he, in fact, was, not that sometime in the future somebody found traces of PCP in his blood.”
Hayes never presented such foundational testimony and, as a result, the jury never heard Dr. Kalish’s opinion testimony. Dr. Kalish was allowed to testify generally as to the effects of PCP, but he was never able to relate this testimony specifically to Hayes.
Relying on Hayes’ blood test taken 18 hours after the shooting—which was the only evidence of PCP use before the jury—defense counsel argued inferentially that Hayes was under the influence of PCP at the time of the shooting. Then, relying on Dr. Kalish’s general testimony regarding the effects of PCP, counsel suggested to the jury that the People had failed to sustain their burden of proving beyond a reasonable doubt that Hayes entertained the mental states of premeditation and malice aforethought necessary to convict him of first degree murder since it was possible the PCP use affected his ability to form these mental states. The prosecutor responded that the blood test in no way indicated Hayes was under the influence of PCP at the time of the shooting; he could have taken PCP at any time during the 18-hour period. Furthermore, the prosecutor emphasized there was no *522evidence indicating that even if Hayes was under the influence of PCP at the time of the shooting, such influence affected his ability to intend and premeditate the killing. The jury found Hayes guilty of premeditated first degree murder.
Hayes then filed a motion for a new trial, alleging he possessed newly discovered evidence which would provide the foundation for Dr. Kalish’s opinion testimony which the court had requested. (See ante, p. 521.) The new evidence was in the form of testimony from Kenneth Hayes (a distant relative of defendant) to the effect that he was with defendant on the evening of the shooting and saw him smoking PCP cigarettes. Kenneth Hayes’ absence from the first trial was explained by his statements that he was in violation of probation at the time he learned a defense investigator was looking for him, and he avoided any contact with the investigator for fear that he would be caught and his probation would be revoked. This information was corroborated in the declaration of the defense investigator, who recounted his numerous attempts to locate Kenneth Hayes prior to the trial.2
The trial judge denied the new trial motion. He determined that “. . . there’s just not quite enough that Mr. Kenneth Hayes could offer that would suffice it to allow the doctor to express an opinion as to the mental state of the defendant. Needless to say, the reason I have hesitated so much is because it’s not all that clear and what is proffered now as being new evidence and in weighing the admission of the doctor or offer of proof as to the doctor’s opinion, I don’t think that he has quite enough to—on the basis of what Kenneth Hayes says, in his affidavit, to support that opinion, so the motion will be denied.”
Discussion
If an expert is asked to give his opinion based on an assumed set of facts, the assumption on which the hypothetical question is based must be supported by evidence in the record. (See Hyatt v. Sierra Boat Co. (1978) 79 Cal.App.3d 325, 338-339 [145 Cal.Rptr. 47]; Witkin, Cal. Evidence (2d ed. 1966) Introduction of Evidence at Trial, § 1180, pp. 1093-1094.) In the present case, the only evidence before the jury regarding Hayes’ PCP use was the blood test taken some 18 hours after the shooting incident. Dr. Kalish himself admitted that there was no way to tell solely from the blood *523test whether Hayes was under the influence of PCP at the time of the shooting. Accordingly, there was no evidence before the jury on which defense counsel could base his assumption that Hayes was under the influence of PCP when he shot Terry Clemons and the trial court properly refused to permit Dr. Kalish’s testimony in response to the hypothetical question.3
Our conclusion that the hypothetical question posed to Dr. Kalish was not properly founded on evidence in the record necessarily implies that had there been such evidence, the opinion testimony would have been admissible. As noted previously, the trial court articulated a similar rationale at the time it ruled Dr. Kalish’s testimony inadmissible; “If there was some evidence that he was under the influence at the time of the shooting, then I think the doctor’s opinion would be admissible . . . .”
The People do not seriously contend that Kenneth Hayes’ testimony, if given at trial, would not provide sufficient foundation for Dr. Kalish’s opinion regarding defendant’s mental state.4 Instead, relying in particular on the Supreme Court’s most recent discussion of motions for new trial based on newly discovered evidence (see People v. Martinez (1984) 36 Cal.3d 816 [205 Cal.Rptr. 852, 685 P.2d 1203]), they argue that Hayes’ motion was nonetheless properly denied.
In this regard, the People first suggest that Kenneth Hayes’ testimony was not “newly discovered.” They contend that both defendant and his counsel knew of the potential significance of Hayes’ testimony as was evidenced by their attempts to locate him prior to trial. Were the “newly *524discovered” requirement interpreted literally and restrictively, this set of facts might pose some concern. But we read the Supreme Court’s decision in People v. Williams (1962) 57 Cal.2d 263, 273-274 [18 Cal.Rptr. 729, 368 P.2d 353] to have rejected such a mechanistic interpretation in favor of a more realistic approach which ties the concept of “newly discovered” evidence to the reasonableness of the defense conduct in failing to present the evidence at the first trial. In Williams, the court reversed an order denying a new trial even though the defendant knew of the “new” witness and her potential testimony before the first trial. (Id., at p. 272.) This approach was reinforced in Martinez, supra, 36 Cal.3d 816, in which the court held that the attorney’s lack of diligence in discovering relevant evidence, as distinguished from the defendant’s, will generally not support the denial of a motion for new trial. (Id., at p. 825.) In the present case, the People do not contend that the failure to present Kenneth Hayes’ testimony at the first trial was the product of defendant’s lack of diligence. Accordingly, we conclude that Kenneth Hayes’ testimony was “newly discovered” evidence within the meanings of Williams and Martinez.5
The People next attempt to argue that Kenneth Hayes’ testimony was “somewhat cumulative.” While recognizing there was no other evidence at trial which remotely duplicated the material contained in Kenneth Hayes’ declaration, the People nonetheless rely on the fact that defendant could have testified to his ingestion of PCP had he so desired. This argument, however, fails to recognize that defendant has a Fifth Amendment privilege not to testify. To deny his motion for new trial based on the fact that he could have presented the same evidence by waiving his Fifth Amendment rights would impermissibly penalize his exercise of those rights. (Cf. Griffin v. California (1965) 380 U.S. 609 [14 L.Ed.2d 106, 85 S.Ct. 1229].)
Finally, the People contend it is not reasonably probable that the testimony of Kenneth Hayes and in turn Dr. Kalish, “had it been presented to the jury, would have affected the outcome of the trial.” (People v. Martinez, supra, 36 Cal.3d at p. 822.) The consideration of this factor on a motion for new trial in essence asks both the trial and appellate courts to determine whether the inability of the defendant to present the evidence in question prejudiced the outcome of the trial. In viewing such an issue, we justifiably accord considerable deference to the trial judge “because of ‘his *525observation of the witnesses, [and] his superior opportunity to get “the feel of the case.”’ [Citation.]” (Hurtado v. Statewide Home Loan Co. (1985) 167 Cal.App.3d 1019, 1024 [213 Cal.Rptr. 712].) In the present case, however, the trial court did not rely on the lack of prejudice in denying Hayes’ new trial motion. In fact, when initially considering the admissibility of Dr. Kalish’s opinion testimony at trial, the judge commented, “[T]he problem is that if it is ultimately deemed inadmissible, it wouldn’t be too much help to the prosecution in allowing it, but if I exclude it and ultimately it’s going to be error, it would be reversible error. ” (Italics added.)
We concur with the trial court’s view of the prejudice to Hayes in not having Dr. Kalish’s opinion presented to the jury. Hayes did not contest that he shot Terry Clemons. His sole defense, by way of mitigation, was that he did not entertain the mental state necessary for premeditated first degree murder. The Supreme Court has recently discussed in a variety of contexts the importance of a defendant’s mental state in determining criminal culpability. (People v. Garcia (1984) 36 Cal.3d 539, 551-552 [205 Cal.Rptr. 265, 684 P.2d 826]; People v. Beeman (1984) 35 Cal.3d 547 [199 Cal.Rptr. 60, 674 P.2d 1318]; Carlos v. Superior Court (1983) 35 Cal.3d 131, 148-152 [197 Cal.Rptr. 79, 672 P.2d 862]; People v. Burroughs (1984) 35 Cal.3d 824, 850 [201 Cal.Rptr. 319, 678 P.2d 894] (conc. opn. of Bird, C. J.).) The importance of mental state in assessing a defendant’s criminal liability necessarily presumes that the jury has before it all evidence relevant to the defendant’s mental state. Here, the trial court ruled that Hayes was unable to present his best evidence on the critical issue in the case. While that ruling was correct when defendant failed to provide a proper foundation for the evidence (see ante, at p. 522), Kenneth Hayes’ testimony provided the necessary link. Dr. Kalish’s testimony would likely have affected the verdict on the issue of premeditation if not on the question of malice.6 By reason of such evidence, “the result could reasonably and probably be different on retrial.” (People v. Shepherd (1936) 14 Cal.App.2d 513, 519 [58 P.2d 970]; quoted in People v. Williams, supra, 57 Cal.2d at p. 275.) Hayes should have the opportunity to present and argue that evidence to the jury.
*526 Accordingly, we conclude the trial court erred in denying Hayes a motion for a new trial.7
Disposition
Judgment reversed.
Butler, J., concurred.
The trial court interpreted defense counsel’s offer of proof regarding Hayes’ ability to entertain the requisite mental state as not running afoul of the recent legislative abolition of the “diminished capacity” defense. (See Pen. Code, §§ 22, subd. (a), 25, subd. (a), and 28.) We assume likewise, and therefore do not address Hayes’ contention that the failure to admit properly founded expert opinion testimony would violate his due process rights to present all evidence in his defense.
Between the conclusion of the trial and the filing of Hayes’ motion for a new trial, Kenneth Hayes was arrested for violating his probation. Probation was reinstated on January 25, 1984. Due to confusion caused by the same last name, Raymond Hayes’ attorney received a phone call from the superior court clerk regarding Kenneth Hayes’ probation hearing. As a result, the attorney located Kenneth Hayes and obtained his declaration in preparation for the motion for new trial.
We are curious as to why defense counsel did not attempt to introduce Dr. Kalish’s clinical opinion that Hayes was under the influence of PCP at the time of the shooting. (See ante, p. 520.) While such opinion was based on matters outside the record, it falls within the general rule that an expert may base his opinion on information “ whether or not admissible, that is of a type that reasonably may be relied upon by an expert in forming an opinion upon the subject to which his testimony relates, ...” (Evid. Code, § 801, subd. (b) (italics added); People v. Mazoros (1977) 76 Cal.App.3d 32, 44 [142 Cal.Rptr. 599].) Such testimony would, of course, have provided sufficient foundation for Dr. Kalish’s further testimony regarding defendant’s mental state at the time of the shooting. In view of our subsequent conclusion that Kenneth Hayes’ testimony as described in his declaration in support of defendant’s motion for new trial would likewise provide sufficient foundation for Dr. Kalish’s opinion testimony, we have no further need to discuss the admissibility of Dr. Kalish’s clinical opinion or the tactical reasons underlying defense counsel’s decision not to seek its admission.
The Attorney General does rely by analogy on two cases dealing with the consumption of alcohol (see People v. Sanchez (1982) 131 Cal.App.3d 718, 735 [182 Cal.Rptr. 671]; People v. Cram (1970) 12 Cal.App.3d 37, 44 [90 Cal.Rptr. 393]) to suggest that Kenneth Hayes’ testimony as to the quantity of PCP ingested (sharing three cigarettes) was insufficient to establish that defendant was under the influence. Dr. Kalish, however, testified as to the unpredictable effects of the drug, even in very small doses. We believe Hayes’ testimony was sufficient to allow Dr. Kalish to give his opinion as to the effect of PCP on defendant’s mental state.
Inexplicably, the People also argue that Kenneth Hayes’ declaration in support of the motion for new trial was not the “best evidence” of the facts it contained because “[although Hayes was apparently brought to court, he never testified.” The deputy district attorney arguing in opposition to the motion for new trial explicitly conceded that “proof by affidavit is the appropriate method of going forward with the motion for new trial in newly discovered evidence. ... So where I state that this is not the best evidence in my original points and authorities, that should be stricken. That is an error.”
Consistent with the Supreme Court’s analysis in People v. Anderson (1968) 70 Cal.2d 15, 26-27 [73 Cal.Rptr. 550, 447 P.2d 942], we think the jury would likely have viewed Dr. Kalish’s testimony as significant on the issue of premeditation. Other than the presence of the gun in the car, which is at best equivocal, there was no evidence of any prior planning activity by Hayes. Evidence of “prior relationship and/or conduct with the victim” was limited to the circumstances of the “sherm stick” transaction; there was no evidence of any prior relationship between Hayes and Clemons which might give rise to a motive for the killing. The prosecution’s best argument was that the “manner of killing” was consistent with a premeditated intent to kill.
For the purposes of retrial, we also note the court instructed the jury pursuant to CALJIC No. 4.20 that “ ‘no act committed by a person while in a state of voluntary intoxication is less criminal by reason of his having been in such condition. ’ [f] In the offense charged in count one, the fact that the defendant was voluntarily intoxicated is not a defense and does not relieve him of responsibility for the crime. ” It is well-established that it is error to give such an instruction in a trial such as the present one which involves a crime requiring a specific mental state. (People v. Spencer (1963) 60 Cal.2d 64, 87 [31 Cal.Rptr. 782, 383 P.2d 134]; People v. Ford (1964) 60 Cal.2d 772, 796 [36 Cal.Rptr. 620, 388 P.2d 892], overruled on other grounds in People v. Satchell (1971) 6 Cal.3d 28 [98 Cal.Rptr. 33, 489 P.2d 1361, 50 A.L.R.3d 383].) The instruction should not be given on retrial.