delivered the opinion of the Court.
The question presented by this criminal cause is one of first impression in this State, and yet, it involves “the oldest of the privileges for confidential communications” — that which exists between an attorney and his client. 8 J. Wigmore, Evidence in Trials at Common Law § 2290, at 542 (McNaughton rev. 1961). Stated succinctly, we are asked to decide whether this privilege was violated when, over objection, a psychiatrist, who was retained by defense counsel to examine his client in preparing an insanity defense, was permitted to testify at the instance of the prosecution. Because we conclude that this fundamental privilege was invaded, we will direct a new trial. 1
The factual background here is uncomplicated and may be briefly related. On the morning of October 23, 1976, respondent Margaret Melton Pratt, after a sleepless night during which she contemplated the taking of her own life, *518 shot and killed her still-slumbering husband, William S. Pratt, in their Montgomery County apartment. After the shooting, the wife packed an overnight bag and drove to a friend’s farm near Front Royal, Virginia, to visit the gravesite of her dog; she stayed several hours and then proceeded to a nearby motel to spend the night. The next morning Mrs. Pratt returned to her home and, after a short stay there, began driving aimlessly around the Bethesda-Rockville area. Realizing she would eventually be apprehended, the respondent went to the Montgomery County police and informed them of her husband’s death. The officers, after verifying Mrs. Pratt’s story concerning what had taken place, arrested her for murder.
Upon being indicted by the grand jury for murder and related offenses, the respondent entered pleas of not guilty and interposed a defense of insanity at the time of the commission of the alleged crimes, as is permitted by Maryland Rule 731 and section 25 of Article 59 of the Maryland Code (1957,1972 Repl. Vol.). Thereafter, the Circuit Court for Montgomery County, as authorized by sections 23 and 25 (b) of Article 59 of the Code (1957, 1972 Repl. Vol.), ordered that the Department of Health and Mental Hygiene conduct a mental examination of Mrs. Pratt to determine her “sanity or insanity at the present time and at the time of the commission of the crime, and ... her competency] to stand trial at the present time____” After an examination, the department, by its report dated December 30,1976, informed the court that Mrs. Pratt was presently competent to stand trial and was sane at the time of the commission of the alleged offenses. Trial on the indictment began on April 18,1977, and three days later the jury found Mrs. Pratt was sane at the time of the commission of the alleged crimes and guilty of both murder in the second degree and the use of a handgun in the commission of a felony.
Throughout the trial, Mrs. Pratt did not dispute that she had killed her husband but, instead, strenuously urged that she was insane at the time she fired the fatal shots. In support of her insanity plea, respondent presented two psychiatrists, Dr. Gerald Polin and Dr. Leon Yochelson, who testified that
*519
at the time of the act Mrs. Pratt was, in their opinion, suffering from a mental illness of such severity that she lacked substantial capacity to conform her conduct to the requirements of the law. See Md. Code (1957, 1972 Repl. Vol.), Art. 59, § 25 (a). In rebuttal, the State produced three psychiatrists, all of whom agreed that the respondent was suffering from some degree of mental disorder when the shooting took place. Nonetheless, two of these medical experts testified that, under Maryland law, Mrs. Pratt was legally responsible for her act. Of these two, one, Dr. Brian Crowley, had examined the accused at the request of her attorney after being retained by him to aid in preparing support for Mrs. Pratt’s insanity plea. It is the evidence given by Dr. Crowley, who testified during the trial at the request of the State and over the objection of the defense, that precipitated the controversy now before us. On appeal to the Court of Special Appeals, that court concluded that the permitting of Dr. Crowley’s testimony violated the attorney-client privilege and ordered a new trial.
Pratt v. State,
In this State the attorney-client privilege, deeply rooted in commow law and now memorialized in section 9-108 of the Maryland Code’s (1974) Courts Article,
2
is a rule of evidence that forever bars disclosure, without the consent of the client, of all communications that pass in confidence between the client and his attorney during the course of professional employment or as an incident of professional intercourse between them.
See Harrison v. State,
Initially we observe that, given the complexities of modern existence, few if any lawyers could, as a practical matter, represent the interest of their clients without a variety of nonlegal assistance. Recognizing this limitation, it is now almost universally accepted in this country that the scope of the attorney-client privilege, at least in criminal causes, embraces those agents whose services are required by the attorney in order that he may properly prepare his client’s case. Consequently, in line with the views of the vast majority of the courts in our sister jurisdictions, we have no hesitancy in concluding that in criminal causes communications made by a defendant to an expert in order to equip that expert with the necessary information to provide the defendant’s attorney with the tools to aid him in giving his client proper legal advice are within the scope of the attorney-client privilege.
E.g., United States v. Alvarez, supra,
The State here does not dispute the inclusion of psychiatric communications within the scope of the attorney-client privilege; instead, it contends that when Mrs. Pratt interposed a defense of insanity, she waived the privilege with respect to all statements she may have made to any medical expert, whether in her employ or in that of the State.
3
While there is little doubt that a client may waive this right to confidentiality, which may be done either expressly or impliedly,
see, e.g., Harrison v. State, supra,
A defendant who seeks to introduce psychiatric testimony in support of his insanity plea may be required to disclose prior to trial the underlying basis of his alleged affliction to a prosecution psychiatrist. Hence, where, as here, a defendant reveals to the prosecution the very facts which would be secreted by the exercise of the privilege, reason does not compel the exclusion of expert testimony based on such facts, or cross-examination concerning the grounds for opinions based thereon. It follows that no harm accrues to the defense from seeking pretrial psychiatric advice where an insanity plea is actually entered, for in such circumstances, the underlying factual basis will be revealed to the prosecution psychiatrist. [People v. Edney,39 N.Y.2d 620 ,350 N.E.2d 400 , 403,385 N.Y.S.2d 23 , 26 (1976) (citations omitted).]
While there appears to be some logic, at least in a technical sense, to New York’s highest court’s reasoning, nonetheless we find that the chilling effect such a result would have upon a client’s willingness to confide in his attorney or any defense-employed consultants requires that we align ourselves with the overwhelming body of authority and reject that court’s conclusion.
See United States v. Alvarez, supra,
Moreover, a further drawback to the New York rule is the prejudice inherent in disclosing to the trier of fact that the source of this adverse testimony is an expert originally employed by the defendant. This factor will almost certainly carry added weight with the jury, which usually is the
*523
prosecution’s principal purpose for producing the defense-employed psychiatrist as a witness.
See United States ex rel. Edney v. Smith, supra,
*524
An additional consequence of the State’s suggested waiver rule, if adopted by us, is that the defense, in essence, would be required to assist the prosecution in discharging its burden of proof. In Maryland, as in most other jurisdictions, the government not only bears the burden of showing that the defendant perpetrated the alleged criminal act, but, once the sanity of the accused has been placed in doubt by the defense, it is also saddled with the ultimate burden of proving, beyond a reasonable doubt, that the defendant was sane at the time he committed the act.
E.g., State v. Evans,
Accordingly, we affirm the judgment of the Court of Special Appeals, which comports with the ruling we make here.
Judgment of the Court of Special Appeals affirmed.
Costs to be paid by Montgomery County.
Notes
. With this ruling it becomes unnecessary that we decide the two other issues raised by the State.
. Section 9-108 of the Courts Article provides:
A person may not be compelled to testify in violation of the attorney-client privilege. [Md. Code (1974), § 9-108 of the Courts Article.]
See also Md. Code (1957, 1976 Repl. Vol.), Art. 27A, § 8 (persons engaged by Public Defender’s Office covered by attorney-client privilege). Section 9-108 is simply the statutory codification of the common-law privilege as recognized in Maryland.
See
Harrison v. State,
. In effect, the State asks us, by judicial decision, to create a waiver of the attorney-client privilege as the General Assembly has done by providing that, in the case of the psychiatrist/psyehologist-patient privilege, if the patient “introduces his mental condition as an element of his claim or defense ...,” the privilege is waived. See Md. Code (1974, 1978 Cum. Supp.), í) 9-109 (d) (3) (i) of the Courts Article,
. Concerning the testimony of Dr. Crowley, the State’s Attorney argued to the jury:
Mr. Heeney [, the defendant’s attorney,] said ho was glad he didn’t use Dr. Crowley. If Dr. Crowley had given a different opinion, Dr. Crowley would have been in here so fast it would have made your head spin and not in my case but in Mr. Heeney’s case. They hired Dr. Crowley. Dr. Crowley was the first defense psychiatrist to see Mrs. Pratt. He said she did not lack substantial capacity.... What do they do after that? They kept looking and finally they found him. How many people didn’t show up here? I don’t know the answer to that. Were there any others we don’t know about? I don’t know. We know they found two. [(Emphasis added.)]
. In reaching the result we do in this case, we confine our holding to criminal causes and specifically reserve for another time the question of the scope of the attorney-client privilege when an attorney hires an expert to aid in the preparation of civil matters. Though an opponent called as his witness at trial an expert appraiser hired by his adversary in City of Baltimore v. Zell,
. This idea that the prosecution should “shoulder the entire load” has also come to be recognized as an underlying rationale for the constitutional privilege against self-incrimination.
See
Tehan v. United States ex rel. Shott,
. A similar fear of conceivably lightening the prosecution’s burden of proving its case in chief has led a number of courts to reject requests by the government for unlimited discovery.
See, e.g.,
United States v. Wright,
