*218 OPINION
By the Court,
Appellant George D. Singleton was convicted of the killing of Carl Arthur Benson in Las Vegas and was sentenced tо life imprisonment without possibility of parole.
The volume of proof of his complicity was abundant. His defense was based almost entirely on that of insanity. The jury, however, accepted the expert testimony that Singleton knew the difference between right and wrong when he committed the killing.
The issues raised on appeal deal not with the weight of the evidence but with certain purported errors.
1. One question concerns the рrivilege of the attorney-client relationship. Robert Archie, an attorney who at one time reprеsented Singleton in matters other than this offense, testified on rebuttal that Singleton was his client during 1970, that it was his opinion thаt Singleton wasn’t always truthful and that he always found Singleton to be a lucid individual. The defense objects that Archie’s tеstimony constituted a violation *219 of the attorney-client privilege. 1 The State, on the other hand, contends that the testimony offered by Mr. Archie dоes not fall within the protection of the attorney-client privilege. We need not decide this question bеcause we hold that Mr. Singleton waived the privilege when he called various attorneys who had previously represented him to testify on the sanity issue. 2 Mr. Singleton placed in issue both his sanity and his credibility and Mr. Archie’s testimony wаs proper rebuttal.
2. Dr. Hess, a clinical psychologist, was called by the defense to testify regarding Singleton’s mental health. He testified that his results were confirmed by earlier tests conducted by Mr. Long. On cross-examinatiоn Dr. Hess was asked if he was aware that Mr. Long’s certificate to act as a psychologist in Nevada wаs under review for allegedly representing that he had certain educational qualifications that he in fact did not have. Appellant objected that this was improper impeachment of the witness.
The question was proper under NRS 50.305.
3
The statutе is dispositive. The credibility of a source used by Dr. Hess in arriving at his opinion was an underlying fact which could be pursuеd on cross-examination. See Hope v. Arrowhead & Puritas Waters, Inc.,
3. Appellant claims prejudicial error for fаilure of the trial court to give certain instructions involving the “state of mind” doctrine. This doctrine was a subject оf discussion by this court in Fox v. State,
Therе is no evidence of tensional circumstances described in Fox, supra, which would compel the court to give the requested instruction. An instruction need not be given when there is no proof in the record to supрort it. State v. Parr,
4. Dr. William O’Gorman, following his initial examination of the defendant, indicated that Singleton’s I.Q. was in the idiot lеvel range but revised his opinion concerning Singleton’s sanity after receiving additional information. Since NRS 194.010 rеmoves idiots, lunatics and insane persons from the class of persons who may be punished for crime, aрpellant contends that O’Gorman’s testimony brought him within the statute.
An idiot is a person destiute of mind at birth or a persоn of such weak and feeble mind existing frojn birth as renders him incapable of knowing right from wrong or, knowing, has not by reasоn of such mental condition the will power to resist. Jones v. Commonwealth,
The record does not support a conclusion that Singleton can be classified as an idiot according to the legal definition. Whether he was able to distinguish right from wrong was adequately covered by the instruction on insanity.
5. Appellant also raises the issue that he was denied equal time in his closing argument to the jury. There is no merit to that contention nor to his objection that Dr. James Clarke, a pathologist, was not competent to testify to the maximum and minimum calibеr weapon that killed the victim. Dr. Clarke’s experience in treating hundreds of gunshot wounds and his familiarity with certain сaliber weapons was sufficient to establish his competency to testify. Cf. People v. Anderson, 518 *221 P.2d 828 (Colo. 1974). Thе competency of an expert is for the trial court to determine and will not be grounds for reversal absent a clear showing of abuse.
Affirmed.
Notes
NRS 49.095: General rule of рrivilege. A client has a privilege to refuse to disclose, and to prevent any other person from disclosing, confidential communications:
1. Between himself or his representative and his lawyer or his lawyer’s reрresentative.
This court does not view favorably the practice of calling attorneys to testify cоncerning their impressions or relationships with clients who have become litigants. This observation is subject, of course, to established exceptions.
NRS 50.305 Disclosure of facts, data underlying expert opinion. The expert may testify in terms of opinion or inference and give his reasons therefor without prior disclosure of the underlying facts or data, unless the judge requires otherwise. The expert may in any event be required to disclose the underlying facts or data on cross-examination.