SUPREME COURT OF THE UNITED STATES -------- No. 95-266 -------- CARRIE JAFFEE, special administrator for RICKY ALLEN, Sr., deceased, PETITIONER v. MARY LU REDMOND et al. on writ of certiorari to the united states court of appeals for the seventh circuit [June 13, 1996] Justice Stevens delivered the opinion of the Court. After a traumatic incident in which she shot and killed a man, a police officer received extensive counsel- ing from a licensed clinical social worker. The question we address is whether statements the officer made to her therapist during the counseling sessions are pro- tected from compelled disclosure in a federal civil action brought by the family of the deceased. Stated otherwise, the question is whether it is appropriate for federal courts to recognize a -psychotherapist privilege- under Rule 501 of the Federal Rules of Evidence. I Petitioner is the administrator of the estate of Ricky Allen. Respondents are Mary Lu Redmond, a former police officer, and the Village of Hoffman Estates, Illinois, her employer during the time that she served on the police force. Petitioner commenced this action against respondents after Redmond shot and killed Allen while on patrol duty. On June 27, 1991, Redmond was the first officer to respond to a -fight in progress- call at an apartment complex. As she arrived at the scene, two of Allen's sisters ran toward her squad car, waving their arms and shouting that there had been a stabbing in one of the apartments. Redmond testified at trial that she relayed this information to her dispatcher and requested an ambulance. She then exited her car and walked toward the apartment building. Before Redmond reached the building, several men ran out, one waving a pipe. When the men ignored her order to get on the ground, Redmond drew her service revolver. Two other men then burst out of the building, one, Ricky Allen, chasing the other. According to Redmond, Allen was brandishing a butcher knife and disregarded her repeated commands to drop the weapon. Redmond shot Allen when she believed he was about to stab the man he was chasing. Allen died at the scene. Redmond testified that before other officers arrived to provide support, -people came pouring out of the buildings,- App. 134, and a threaten- ing confrontation between her and the crowd ensued. Petitioner filed suit in Federal District Court alleging that Redmond had violated Allen's constitutional rights by using excessive force during the encounter at the apartment complex. The complaint sought damages under Rev. Stat. 1979, 42 U. S. C. 1983 and the Illinois wrongful death statute, Ill. Comp. Stat., ch. 740, 180/1 et seq. (1994). At trial, petitioner presented testimony from members of Allen's family that conflicted with Redmond's version of the incident in several important respects. They testified, for example, that Redmond drew her gun before exiting her squad car and that Allen was unarmed when he emerged from the apartment building. During pretrial discovery petitioner learned that after the shooting Redmond had participated in about 50 counseling sessions with Karen Beyer, a clinical social worker licensed by the State of Illinois and employed at that time by the Village of Hoffman Estates. Petitioner sought access to Beyer's notes concerning the sessions for use in cross-examining Redmond. Respondents vigorously resisted the discovery. They asserted that the contents of the conversations between Beyer and Red- mond were protected against involuntary disclosure by a psychotherapist-patient privilege. The district judge rejected this argument. Neither Beyer nor Redmond, however, complied with his order to disclose the contents of Beyer's notes. At depositions and on the witness stand both either refused to answer certain questions or professed an inability to recall details of their conversations. In his instructions at the end of the trial, the judge advised the jury that the refusal to turn over Beyer's notes had no -legal justification- and that the jury could therefore presume that the contents of the notes would have been unfavorable to respondents. The jury awarded petitioner $45,000 on the federal claim and $500,000 on her state-law claim. The Court of Appeals for the Seventh Circuit reversed and remanded for a new trial. Addressing the issue for the first time, the court concluded that -reason and experience,- the touchstones for acceptance of a privilege under Rule 501 of the Federal Rules of Evidence, com- pelled recognition of a psychotherapist-patient privilege. 51 F. 3d 1346, 1355 (1995). -Reason tells us that psychotherapists and patients share a unique relation- ship, in which the ability to communicate freely without the fear of public disclosure is the key to successful treatment.- Id., at 1355-1356. As to experience, the court observed that all 50 States have adopted some form of the psychotherapist-patient privilege. Id., at 1356. The court attached particular significance to the fact that Illinois law expressly extends such a privilege to social workers like Karen Beyer. Id., at 1357. The court also noted that, with one exception, the federal decisions rejecting the privilege were more than five years old and that the -need and demand for counseling services has skyrocketed during the past several years.- Id., at 1355-1356. The Court of Appeals qualified its recognition of the privilege by stating that it would not apply if -in the interests of justice, the evidentiary need for the disclo- sure of the contents of a patient's counseling sessions outweighs that patient's privacy interests.- Id., at 1357. Balancing those conflicting interests, the court observed, on the one hand, that the evidentiary need for the contents of the confidential conversations was diminished in this case because there were numerous eyewitnesses to the shooting, and, on the other hand, that Officer Redmond's privacy interests were substantial. Id., at 1358. Based on this assessment, the court concluded that the trial court had erred by refusing to afford protection to the confidential communications between Redmond and Beyer. The United States courts of appeals do not uniformly agree that the federal courts should recognize a psycho- therapist privilege under Rule 501. Compare In re Doe, 964 F. 2d 1325 (CA2 1992) (recognizing privilege); In re Zuniga, 714 F. 2d 632 (CA6), cert. denied, 464 U. S. 983 (1983) (same), with United States v. Burtrum, 17 F. 3d 1299 (CA10), cert. denied, 513 U. S. ___ (1994) (declin- ing to recognize privilege); In re Grand Jury Proceedings, 867 F. 2d 562 (CA9), cert. denied sub nom. Doe v. United States, 493 U. S. 906 (1989) (same); United States v. Corona, 849 F. 2d 562 (CA11 1988), cert. denied, 489 U. S. 1084 (1989) (same); United States v. Meagher, 531 F. 2d 752 (CA5), cert. denied, 429 U. S. 853 (1976) (same). Because of the conflict among the courts of appeals and the importance of the question, we granted certiorari. 516 U. S. ___ (1995). We affirm. II Rule 501 of the Federal Rules of Evidence authorizes federal courts to define new privileges by interpreting -common law principles . . . in the light of reason and experience.- The authors of the Rule borrowed this phrase from our opinion in Wolfle v. United States, 291 U. S. 7, 12 (1934), which in turn referred to the oft- repeated observation that -the common law is not im- mutable but flexible, and by its own principles adapts itself to varying conditions.- Funk v. United States, 290 U. S. 371, 383 (1933). See also Hawkins v. United States, 358 U. S. 74, 79 (1958) (changes in privileges may be -dictated by `reason and experience'-). The Senate Report accompanying the 1975 adoption of the Rules indicates that Rule 501 -should be understood as reflecting the view that the recognition of a privilege based on a confidential relationship . . . should be determined on a case-by-case basis.- S. Rep. No. 93- 1277, p. 13 (1974). The Rule thus did not freeze the law governing the privileges of witnesses in federal trials at a particular point in our history, but rather directed federal courts to -continue the evolutionary development of testimonial privileges.- Trammel v. United States, 445 U. S. 40, 47 (1980); see also Univer- sity of Pennsylvania v. EEOC, 493 U. S. 182, 189 (1990). The common-law principles underlying the recognition of testimonial privileges can be stated simply. -`For more than three centuries it has now been recognized as a fundamental maxim that the public . . . has a right to every man's evidence. When we come to examine the various claims of exemption, we start with the primary assumption that there is a general duty to give what testimony one is capable of giving, and that any exemp- tions which may exist are distinctly exceptional, being so many derogations from a positive general rule.'- United States v. Bryan, 339 U. S. 323, 331 (1950) (quoting 8 J. Wigmore, Evidence 2192, p. 64 (3d ed. 1940)). See also United States v. Nixon, 418 U. S. 683, 709 (1974). Exceptions from the general rule disfavoring testimonial privileges may be justified, however, by a -`public good transcending the normally predominant principle of utilizing all rational means for ascertaining the truth.'- Trammel, 445 U. S., at 50, quoting Elkins v. United States, 364 U. S. 206, 234 (1960) (Frankfurter, J., dissenting). Guided by these principles, the question we address today is whether a privilege protecting confidential communications between a psychotherapist and her patient -promotes sufficiently important interests to outweigh the need for probative evidence . . . .- 445 U. S., at 51. Both -reason and experience- persuade us that it does. III Like the spousal and attorney-client privileges, the psychotherapist-patient privilege is -rooted in the imperative need for confidence and trust.- Trammel, 445 U. S., at 51. Treatment by a physician for physical ailments can often proceed successfully on the basis of a physical examination, objective information supplied by the patient, and the results of diagnostic tests. Effective psychotherapy, by contrast, depends upon an atmosphere of confidence and trust in which the patient is willing to make a frank and complete disclosure of facts, emotions, memories, and fears. Because of the sensitive nature of the problems for which individuals consult psychothera- pists, disclosure of confidential communications made during counseling sessions may cause embarrassment or disgrace. For this reason, the mere possibility of disclosure may impede development of the confidential relationship necessary for successful treatment. As the Judicial Conference Advisory Committee observed in 1972 when it recommended that Congress recognize a psychotherapist privilege as part of the Proposed Federal Rules of Evidence, a psychiatrist's ability to help her patients -is completely dependent upon [the patients'] willing- ness and ability to talk freely. This makes it dif- ficult if not impossible for [a psychiatrist] to func- tion without being able to assure . . . patients of confidentiality and, indeed, privileged communica- tion. Where there may be exceptions to this general rule . . . , there is wide agreement that confidential- ity is a sine qua non for successful psychiatric treatment.- Advisory Committee's Notes to Proposed Rules, 56 F. R. D. 183, 242 (1972) (quoting Group for Advancement of Psychiatry, Report No. 45, Confidentiality and Privileged Communication in the Practice of Psychiatry 92 (June 1960)). By protecting confidential communications between a psychotherapist and her patient from involuntary disclosure, the proposed privilege thus serves important private interests. Our cases make clear that an asserted privilege must also -serv[e] public ends.- Upjohn Co. v. United States, 449 U. S. 383, 389 (1981). Thus, the purpose of the attorney-client privilege is to -encourage full and frank communication between attorneys and their clients and thereby promote broader public interests in the observ- ance of law and administration of justice.- Ibid. And the spousal privilege, as modified in Trammel, is justi- fied because it -furthers the important public interest in marital harmony,- 445 U. S., at 53. See also United States v. Nixon, 418 U. S., at 705; Wolfle v. United States, 291 U. S., at 14. The psychotherapist privilege serves the public interest by facilitating the provision of appropriate treatment for individuals suffering the effects of a mental or emotional problem. The mental health of our citizenry, no less than its physical health, is a public good of transcendent importance. In contrast to the significant public and private interests supporting recognition of the privilege, the likely evidentiary benefit that would result from the denial of the privilege is modest. If the privilege were rejected, confidential conversations between psycho- therapists and their patients would surely be chilled, particularly when it is obvious that the circumstances that give rise to the need for treatment will probably result in litigation. Without a privilege, much of the desirable evidence to which litigants such as petitioner seek access-for example, admissions against interest by a party-is unlikely to come into being. This unspoken -evidence- will therefore serve no greater truth-seeking function than if it had been spoken and privileged. That it is appropriate for the federal courts to recog- nize a psychotherapist privilege under Rule 501 is confirmed by the fact that all 50 States and the District of Columbia have enacted into law some form of psycho- therapist privilege. We have previously observed that the policy decisions of the States bear on the question whether federal courts should recognize a new privilege or amend the coverage of an existing one. See Trammel, 445 U. S., at 48-50; United States v. Gillock, 445 U. S. 360, 368, n. 8 (1980). Because state legislatures are fully aware of the need to protect the integrity of the factfinding functions of their courts, the existence of a consensus among the States indicates that -reason and experience- support recognition of the privilege. In addition, given the importance of the patient's under- standing that her communications with her therapist will not be publicly disclosed, any State's promise of confidentiality would have little value if the patient were aware that the privilege would not be honored in a fed- eral court. Denial of the federal privilege therefore would frustrate the purposes of the state legislation that was enacted to foster these confidential communications. It is of no consequence that recognition of the privilege in the vast majority of States is the product of legisla- tive action rather than judicial decision. Although common-law rulings may once have been the primary source of new developments in federal privilege law, that is no longer the case. In Funk v. United States, 290 U. S. 371 (1933), we recognized that it is appropriate to treat a consistent body of policy determinations by state legislatures as reflecting both -reason- and -experience.- Id., at 376-381. That rule is properly respectful of the States and at the same time reflects the fact that once a state legislature has enacted a privilege there is no longer an opportunity for common-law creation of the protection. The history of the psychotherapist privilege illustrates the latter point. In 1972 the members of the Judicial Conference Advisory Committee noted that the common law -had indicated a disposition to recognize a psychotherapist-patient privilege when legislatures began moving into the field.- Proposed Rules, 56 F. R. D., at 242 (citation omitted). The present unanimous accep- tance of the privilege shows that the state lawmakers moved quickly. That the privilege may have developed faster legislatively than it would have in the courts demonstrates only that the States rapidly recognized the wisdom of the rule as the field of psychotherapy developed. The uniform judgment of the States is reinforced by the fact that a psychotherapist privilege was among the nine specific privileges recommended by the Advisory Committee in its proposed privilege rules. In United States v. Gillock, 445 U. S. 360, 367-368 (1980), our holding that Rule 501 did not include a state legislative privilege relied, in part, on the fact that no such privilege was included in the Advisory Committee's draft. The reasoning in Gillock thus supports the opposite conclusion in this case. In rejecting the proposed draft that had specifically identified each privilege rule and substituting the present more open- ended Rule 501, the Senate Judiciary Committee explicitly stated that its action -should not be under- stood as disapproving any recognition of a psychiatrist- patient . . . privileg[e] contained in the [proposed] rules.- S. Rep. No. 93-1277, at 13. Because we agree with the judgment of the state legislatures and the Advisory Committee that a psycho- therapist-patient privilege will serve a -public good transcending the normally predominant principle of utilizing all rational means for ascertaining truth,- Trammel, 445 U. S., at 50, we hold that confidential communications between a licensed psychotherapist and her patients in the course of diagnosis or treatment are protected from compelled disclosure under Rule 501 of the Federal Rules of Evidence. IV All agree that a psychotherapist privilege covers confi- dential communications made to licensed psychiatrists and psychologists. We have no hesitation in concluding in this case that the federal privilege should also extend to confidential communications made to licensed social workers in the course of psychotherapy. The reasons for recognizing a privilege for treatment by psychiatrists and psychologists apply with equal force to treatment by a clinical social worker such as Karen Beyer. Today, social workers provide a significant amount of mental health treatment. See, e.g., U. S. Dept. of Health and Human Services, Center for Mental Health Services, Mental Health, United States, 1994 pp. 85-87, 107-114; Brief for National Association of Social Workers et al. as Amici Curiae 5-7 (citing authorities). Their clients often include the poor and those of modest means who could not afford the assistance of a psychiatrist or psycholo- gist, id., at 6-7 (citing authorities), but whose counseling sessions serve the same public goals. Perhaps in recognition of these circumstances, the vast majority of States explicitly extend a testimonial privilege to licensed social workers. We therefore agree with the Court of Appeals that -[d]rawing a distinction between the counseling provided by costly psychotherapists and the counseling provided by more readily accessible social workers serves no discernible public purpose.- 51 F. 3d, at 1358, n. 19. We part company with the Court of Appeals on a separate point. We reject the balancing component of the privilege implemented by that court and a small number of States. Making the promise of confidenti- ality contingent upon a trial judge's later evaluation of the relative importance of the patient's interest in privacy and the evidentiary need for disclosure would eviscerate the effectiveness of the privilege. As we explained in Upjohn, if the purpose of the privilege is to be served, the participants in the confidential conver- sation -must be able to predict with some degree of cer- tainty whether particular discussions will be protected. An uncertain privilege, or one which purports to be cer- tain but results in widely varying applications by the courts, is little better than no privilege at all.- 449 U. S., at 393. These considerations are all that is necessary for decision of this case. A rule that authorizes the recogni- tion of new privileges on a case-by-case basis makes it appropriate to define the details of new privileges in a like manner. Because this is the first case in which we have recognized a psychotherapist privilege, it is neither necessary nor feasible to delineate its full contours in a way that would -govern all conceivable future questions in this area.- Id., at 386. V The conversations between Officer Redmond and Karen Beyer and the notes taken during their counseling sessions are protected from compelled disclosure under Rule 501 of the Federal Rules of Evidence. The judg- ment of the Court of Appeals is affirmed. It is so ordered.