Like the majority, I would have no difficulty concluding, under the facts presented, that the entry of an employee of the Lake County Department of Mental Health into Susan T.’s home to “take some pictures as evidence” constituted a search under the Fourth Amendment. I also concur in the judgment, because, like the Court of Appeal, I believe the admission of the photographic evidence was harmless error. Unlike the majority, however, I conclude that the exclusionary rule should apply in conservatorship proceedings under the Lanterman-PetrisShort Act (LPS Act). (Welf. & Inst. Code, § 5000 et seq.)1
“[T]he ‘basic purpose of [the Fourth] Amendment. . . is to safeguard the privacy and security of individuals against arbitrary invasions by governmental officials.’ ” (Michigan v. Tyler (1978) 436 U.S. 499, 504 [56 L.Ed.2d 486, 495, 98 S.Ct. 1942], quoting Camara v. Municipal Court (1967) 387 U.S. 523, 528 [18 L.Ed.2d 930, 935, 87 S.Ct. 1727].) The Supreme Court has emphasized the “ ‘overriding respect for the sanctity of the home that has been embedded in our traditions since the origin of the Republic.’ ” (Oliver v. United States (1984) 466 U.S. 170, 178 [80 L.Ed.2d 214, 224, 104 S.Ct. 1735], quoting Payton v. New York (1980) 445 U.S. 573, 601 [63 L.Ed.2d 639, 659-660, 100 S.Ct. 1371].) Susan T. did not lose the right to privacy and security when she was taken into custody by the Lake County Sheriff under section 5150. Indeed, the LPS Act expressly provides that “[p]ersons with mental illness have the same legal rights and responsibilities guaranteed all other persons by the Federal Constitution and laws and the Constitution and laws of the State of California”—including the right to privacy. (§ 5325.1, subd. (b); see also Conservatorship of Roulet (1979) 23 Cal.3d 219, 224 [152 Cal.Rptr. 425, 590 P.2d 1].)
The exclusionary rule has as its purpose deterrence of unlawful governmental intrusion into the right of personal privacy. (See United States v. Calandra (1974) 414 U.S. 338, 347 [38 L.Ed.2d 561, 571, 94 S.Ct. 613]; United States v. Janis (1976) 428 U.S. 433, 458, fn. 35 [49 L.Ed.2d 1046, 1063, 96 S.Ct. 3021].) As the Supreme Court stressed in first articulating the rule, if evidence seized in violation of the Fourth Amendment can be used in evidence against a citizen accused of an offense “the protection of the Fourth Amendment declaring his right to be secure against such searches and seizures is of no value, and, so far as those thus placed are concerned, might as well be stricken from the Constitution.” (Weeks v. United States (1914) 232 U.S. 383, 393 [58 L.Ed. 652, 656, 34 S.Ct. 341].)
Although it is most commonly applied in the context of criminal proceedings, our courts have applied the exclusionary rule in a variety of civil and *1022administrative proceedings. (See, e.g., People v. One 1960 Cadillac Coupe (1964) 62 Cal.2d 92, 96-97 [41 Cal.Rptr. 290, 396 P.2d 706] [civil forfeiture]; Goldin v. Public Utilities Commission (1979) 23 Cal.3d 638, 669 [153 Cal.Rptr. 802, 592 P.2d 289] [Public Utilities Commission hearing]; Elder v. Bd. of Medical Examiners (1966) 241 Cal.App.2d 246, 260 [50 Cal.Rptr. 304] [administrative proceeding to revoke medical license]; People v. Moore (1968) 69 Cal.2d 674, 682 [72 Cal.Rptr. 800, 446 P.2d 800], overruled on other grounds, People v. Thomas (1977) 19 Cal.3d 630, 637 [139 Cal.Rptr. 594, 566 P.2d 228] [civil commitment proceedings for narcotic addicts]; see also 1 LaFave, Search & Seizure (2d ed. 1987) § 1.7(e), pp. 158-159 (LaFave) [citing cases applying the exclusionary rule in Federal Trade Commission hearings, Securities and Exchange Commission proceedings, Occupational Safety and Health Administration proceedings, proceedings before the Public Utilities Commission, National Labor Relations Board hearings, and other civil and administrative proceedings].)
In considering whether to apply the exclusionary rule in civil cases, courts apply a balancing test. (See People v. Moore, supra, 69 Cal.2d at p. 681; Emslie v. State Bar (1974) 11 Cal.3d 210, 227-228 [113 Cal.Rptr. 175, 520 P.2d 991]; INS v. Lopez-Mendoza (1984) 468 U.S. 1032, 1041 [82 L.Ed.2d 778, 787, 104 S.Ct. 3479].) Three considerations are of particular concern; the magnitude of the consequences for the individual involved, the extent to which exclusion would deter illegal searches and seizures, and the potential social cost of applying the rule. I believe the balance of these factors weighs unequivocally in favor of applying the exclusionary rule to LPS conservatorship proceedings.
A. Magnitude of Consequences for Potential Conservatees
Although not a criminal proceeding, conservatorship proceedings under the LPS Act may result in “a massive curtailment of liberty” (Humphrey v. Cady (1972) 405 U.S. 504, 509 [31 L.Ed.2d 394, 402, 92 S.Ct. 1048]) as severe as that faced by a criminal defendant.2 As Justice Brennan emphasized, “[p]ersons incarcerated in mental hospitals are not only deprived of their physical liberty, they are also deprived of friends, family, and community. Institutionalized mental patients must live in unnatural surroundings under the continuous and detailed control of strangers. They are subject to intrusive treatment which, especially if unwarranted, may violate their right *1023to bodily integrity .... Furthermore . . . persons confined in mental institutions are stigmatized as sick and abnormal during confinement and, in some cases, even after release.” (Parham v. J.R. (1979) 442 U.S. 584, 626-627 [61 L.Ed.2d 101, 133-134, 99 S.Ct. 2493] (conc. & dis. opn. of Brennan, J.), fn. omitted.)
Because involuntary confinement for mental illness, whether civil or criminal, involves a loss of liberty and substantial stigma, we have extended many of the same protections to potential conservatees as to criminal defendants. Thus, we have required that the facts triggering confinement be proved to a unanimous jury beyond a reasonable doubt. (Conservatorship of Roulet, supra, 23 Cal.3d 219; Conservatorship of Hofferber (1980) 28 Cal.3d 161, 178 [167 Cal.Rptr. 854, 616 P.2d 836].) Similarly, a proposed conservatee has the right to confront witnesses and to introduce evidence, and the right to appointed counsel and to free transcripts if indigent. (Conservatorship of Baber (1984) 153 Cal.App.3d 542, 550 [200 Cal.Rptr. 262]; Waltz v. Zumwalt (1985) 167 Cal.App.3d 835, 839 [213 Cal.Rptr. 529].) Wende review (People v. Wende (1979) 25 Cal.3d 436 [158 Cal.Rptr. 839, 600 P.2d 1071]) is also required if appointed appellate counsel finds no arguable issues or describes the appeal of an LPS Act conservatee as frivolous. (Conservatorship of Besoyan (1986) 181 Cal.App.3d 34, 38 [226 Cal.Rptr. 196].) The rationale for these decisions derives, in part, from our recognition that “the interests involved in civil commitment proceedings are no less fundamental than those in criminal proceedings and that liberty is no less precious because forfeited in a civil proceeding than when taken as a consequence of a criminal conviction.” (In re Gary W. (1971) 5 Cal.3d 296, 307 [96 Cal.Rptr. 1, 486 P.2d 1201].)
The LPS Act and decisional law thus contemplate an adversarial proceeding in which the potential conservatee who opposes conservatorship is entitled to the assistance of counsel and many of the procedural rights of a criminal defendant. The majority’s conclusion that there is no similarity between the aims and objectives of the act and those of criminal law is inconsistent with our repeated recognition that involuntary commitment proceedings involve similar considerations to criminal process because, like criminal defendants, potential conservatees are threatened with loss of liberty and social stigma.
Moreover, the fact that conservatorship proceedings are designed to protect rather than punish the conservatee does not detract from the serious curtailment of liberty that results from a finding of “grave disability” under the LPS Act. “ ‘ “Regardless of the purposes for which the incarceration is *1024imposed, the fact remains that it is incarceration. The rehabilitative goals of the system are admirable, but they do not change the drastic nature of the action that has been taken.” ’ ” (Conservatorship of Roulet, supra, 23 Cal.3d at p. 225, quoting Breed v. Jones (1975) 421 U.S. 519, 530, fn. 12 [44 L.Ed.2d 346, 536, 95 S.Ct. 1779].) In addition to the possibility of indefinite placement in a locked psychiatric facility—possibly the same facility used to house criminal defendants—a conservatee faces the loss of important legal rights and privileges, including the rights to enter contracts, to vote, to refuse or consent to medical treatment, including routine medical treatment for conditions unrelated to the conservatee’s grave disability, and the privilege of possessing a driver’s license. (§ 5357.)
In the analogous case of People v. Moore, we expressly rejected the argument that violations of the Fourth and Fourteenth Amendments should be condoned because involuntary commitment (in that case for narcotic addicts) was beneficent rather than punitive. (People v. Moore, supra, 69 Cal.2d at p. 682.) We concluded that to hold unconstitutionally obtained evidence admissible in commitment proceedings would furnish an incentive to conduct unreasonable searches and seizures. Accordingly, we held that the exclusionary rule applied to narcotics addict proceedings. (Ibid.)
I can see no principled basis for distinguishing Moore from the present case. I am unpersuaded by the majority’s attempt to distinguish Moore on the ground that imposition of a conservatorship does not depend on a charged or uncharged criminal act. Moore did not turn on the possibility that a narcotics addict was engaged in criminal activity. Instead, we applied the exclusionary rule on the basis that involuntary civil commitment under section 3000 et seq. “has some of the features pertinent to a criminal case in view of the facts that the state is the defendant’s opponent, that the proceeding is commenced on petition of the district attorney . . . , that the defendant is entitled to be present at the hearing and to be represented by counsel at all stages of the proceeding . . . , that if he is financially unable to employ counsel he is entitled to appointed counsel . . . and that his liberty is at stake.” (People v. Moore, supra, 69 Cal.2d at p. 681, citations omitted.)
Each of these features—along with other features analogous to criminal proceedings discussed, ante—is present in LPS conservatorship hearings. Thus, under the LPS Act a person may be taken into custody by a police officer or designated health officer on probable cause (§5150 [cf. §3100.6]); the establishment of a conservatorship is initiated by the state, with the conservatorship proceedings being brought by the district attorney (§5114 [cf. § 3100]); potential conservatees are entitled to appointed counsel (§5364 [cf. § 3104]) and free appeal transcript (Waltz v. *1025Zumwalt, supra, 167 Cal.App.3d 835 [cf. People v. Moore, supra, 69 Cal.2d at p. 681]); and the liberty of potential conservatees is clearly at stake (§5358 [cf. §3106]).
An additional consideration in LPS proceedings is the high risk of error. We have repeatedly stressed the uncertainties that surround psychiatric diagnoses and the concomitant risk that a person will be wrongly subjected to the loss of liberty and reputation in commitment proceedings. (Conservatorship of Roulet, supra, 23 Cal.3d 219, 230; People v. Burnick (1975) 14 Cal.3d 306, 327 [121 Cal.Rptr. 488, 535 P.2d 352].) Federal courts, too, have expressed concern about the high risk of error in involuntary commitment proceedings. “The risk of error in all mental health decisions is substantial. Even when a standard requires a specific finding of dangerousness, there is great risk of error. ... As Chief Justice Burger wrote in his concurring opinion in O’Connor v. Donaldson . . . ‘[t]here can be little responsible debate regarding “the uncertainty of diagnosis in this field and the tentativeness of professional judgment.” ’ ” (Doe v. Gallinot (C.D.Cal. 1979) 486 F.Supp. 983, 992, affd. 657 F.2d 1017 (9th Cir. 1981), quoting O’Connor v. Donaldson (1975) 422 U.S. 563, 584 [45 L.Ed.2d 396, 412, 95 S.Ct. 2486] (conc. opn. of Burger, C. J.); see also Ennis & Litwack, Psychiatry and the Presumption of Expertise: Flipping Coins in the Courtroom (1974) 62 Cal.L.Rev. 693; Morse, Crazy Behavior, Morals and Science: An Analysis of Mental Health Law (1978) 51 So.Cal.L.Rev. 527; Morse, A Preference for Liberty: The Case Against Involuntary Commitment of the Mentally Disordered (1982) 70 Cal.L.Rev. 54.)
In People v. Burnick, I quoted Professor Wigmore’s observation that [t]he mental condition of one whose mind is so deranged as to require imprisonment for his own and others’ good is indeed pitiable. But the mental attitude of one who is falsely found insane and relegated to life imprisonment is beyond conception. No greater cruelty can be committed in the name of the law.’ ” (14 Cal.3d at pp. 309-310 (opn. by Mosk, J.), quoting 5 Wigmore on Evidence (Chadboum rev. 1974) § 1400, p. 201).) That observation remains apt despite the efforts by the Legislature to include safeguards for individuals subjected to involuntary commitment proceedings under the LPS Act. (See also Rosenhan, On Being Sane in Insane Places (1973) 13 Santa Clara L.Rev. 379, 382-384; Morris, Conservatorship for the “Gravely Disabled”: California’s Nondeclaration of Nonindependence (1978) 15 San Diego L.Rev. 201.)
As the Court of Appeal held below, the subjective nature of the criteria pertinent to the decision to begin a commitment procedure, as well as the *1026uncertain relationship between mental disorder and legal incompetence, increase the possibility that the administrative decision to conduct a search may be misguided or result from “caprice or . . . personal or political spite” (Eaton v. Price (1960) 364 U.S. 263, 271 [4 L.Ed.2d 1708, 1713, 80 S.Ct. 1463]) or be a subterfuge for a criminal investigation. (See Abel v. United States (1960) 362 U.S. 217, 239-240 [4 L.Ed.2d 668, 686-687, 80 S.Ct. 683].) Thus, application of the exclusionary rule in EPS Act conservatorship proceedings would deter governmental intrusions on personal privacy that may be just as pernicious as the activities the exclusionary rule is designed to deter in criminal cases.
B. Deterrence
The exclusionary rule is based on the principle that the state should not profit from its own wrong in using evidence obtained by unconstitutional methods. (Emslie v. State Bar, supra, 11 Cal.3d 210, 226-227.) Accordingly, a key consideration in determining whether the exclusionary rule should apply is the extent to which exclusion would deter unconstitutional searches and seizures. (Ibid.) The majority conclude that the deterrent effect of applying the exclusionary rule in EPS Act conservatorship cases is merely theoretical. I disagree.
The deterrence argument for exclusion is most compelling when “the administrative agency in question has an investigative function and investigative personnel of that agency participated in the illegal activity for the purpose of providing information to support administrative proceedings against the suspect.” (1 LaFave, supra, at p. 161, fn. omitted.) Here, the same mental health officials who ordered and conducted the search for evidence in Susan T.’s home sought to use the fruits of the search (the photographs) at the EPS conservatorship proceedings. Indeed, under the EPS Act, mental health officials are statutorily required to act as evidence-gatherers and witnesses against the prospective conservatee. (§5150.) The deterrent effect of applying the exclusionary rule in this and other EPS Act conservatorship proceedings would thus be direct. If mental health officials know that evidence obtained in illegal searches will be excluded in conservatorship proceedings, they will have a strong disincentive to conducting searches without obtaining a warrant.
The majority concede that the deterrent effect of the rule is at its greatest when, as is true here, the government agency that effected the search is the same agency that seeks to introduce the fruits of its search at trial. They surmise, however, that precluding the use of evidence in a conservatorship *1027proceeding might have little or no deterrent effect on a mental health worker interested in securing interim treatment under the act under the 14-day or 30-day certifications (§§ 5250, 5270.15), as to which the exclusionary rule may not apply. From this the majority conclude that the deterrence value would be limited. I disagree.
Unlike Lopez-Mendoza, on which the majority rely, this is not a situation in which the rarity of challenges to proceedings weakens the deterrent effect of the rule. (INS v. Lopez-Mendoza, supra, 468 U.S. 1032.) Indeed, the rate of contested conservatorship hearings is apparently substantial. Certainly, even if, as the majority conjecture, some mental health workers may be interested in securing only interim treatment for a detainee, there is no reason to conclude that conservatorship proceedings are so unusual that mental health workers would as a general rule be heedless of the privacy rights of detainees regardless of the exclusionary rule.
The majority also reason that the deterrent value of applying the exclusionary rule is weakened in conservatorship trials because by that stage of the involuntary commitment process the “most relevant” evidence of disability will be derived from the detainee herself. Again, I disagree. A detainee’s living conditions prior to being taken into custody are clearly pertinent to a determination that he or she is “gravely disabled,” i.e., “unable to provide for his or her basic personal needs for food, clothing, or shelter.” (§ 5008, subd. (h)(1)(A).) In this case, the photographic evidence was cumulative, but it was undoubtedly “relevant” and the motion to suppress was vigorously opposed by respondent Lake County Mental Health Department. In my view, there is substantial reason to conclude that the deterrent effect of applying the exclusionary rule in cases such as this would be real, and not merely theoretical.
C. Social Costs
The social costs of applying the exclusionary rule to LPS conservatorship proceedings are minimal. Once aware of the warrant requirement, department employees will have a significant incentive to respect the privacy rights of detainees.3 There is no reason to think that important evidence will be lost or destroyed if mental health authorities are required to obtain *1028a warrant before entering the home of a person thought to be gravely disabled.4
In the unusual event that a search is conducted in violation of the constitutional requirement, it is unlikely that the trier of fact would be seriously hampered in reaching a rational conclusion about the potential conservatee’s mental condition. Contrary to the majority’s conclusion, a court applying the exclusionary rule would not be required to ignore the existence of a continuing state of grave disability. The trier of fact will have the opportunity to hear evidence presented by the mental health professionals who administered the mandatory psychiatric evaluations and treatment of the proposed conservatee (§ 5152 [evaluation during 72-hour hold under § 5150]; § 5251 et seq. [certification for intensive treatment]; § 5260 [confinement for additional treatment]). The court also receives, and may enter into evidence, a comprehensive written report mandated by the act, which must contain “all relevant aspects of the person’s medical, psychological, financial, family, vocational and social condition, and information obtained from the person’s family members, close friends, social worker or principal therapist.” (§ 5354.) Moreover, as this case demonstrates, evidence may also be presented by other percipient witnesses, including family and neighbors. The proposed conservatee may also be required to testify at the conservator-ship trial. (See Conservatorship of Baber, supra, 153 Cal.App.3d at p. 550 [proposed conservatee cannot refuse to testify at conservatorship proceeding].)
Thus, the LPS Act itself reduces the risk that a gravely disabled person will be released without imposition of a conservatorship. Indeed, as the majority observe, the longer a detainee remains in treatment under the interim involuntary commitment provisions of the act, the less need the department will have to rely on extrinsic evidence to demonstrate grave disability. Precisely because LPS Act conservatorship proceedings involve a continuing state of grave disability and not a single act, the social costs of requiring mental health workers to comply with the constitutional limits on the invasion of personal privacy are minimized. Moreover, unlike criminal proceedings in which the risk is that a guilty person will be set free, in the LPS Act context a person released can be detained again if she exhibits new behavior demonstrating grave disability as a result of a mental disorder. (See Conservatorship of Baber, supra, 153 Cal.App.3d at pp. 549-550 [double jeopardy doctrine inapplicable in LPS conservatorship proceedings].)
*1029A person detained under the LPS Act, like all other citizens, has a reasonable expectation of privacy in the sanctity of her home. Although the goals of the LPS Act are beneficent, the loss of liberty and reputation to a conservatee is grave. Weighing the costs and benefits, I can see no basis for ignoring the fundamental guarantees against unreasonable searches and seizures in conducting investigations of potential conservatees. Accordingly, I would apply the exclusionary rule to LPS Act conservatorship proceedings.
All statutory references are to the Welfare and Institutions Code.
The court order establishing a conservatorship may grant the conservator the authority to place the conservatee in a mental facility (§ 5358, subd. (a)) and to require the conservatee to undergo treatment (§ 5358, subd. (b)). An LPS conservatorship lasts for one year but may be reestablished for succeeding one-year periods. (§ 5361.)
Indeed, the San Francisco Public Defender observed that searches like the one at issue here have been infrequent “because it is clear that you need a warrant to get into a house. To even seize a dog you need an administrative warrant.” (Ziegler, Exclusionary Rule Applies in Commitment, San Francisco Daily Journal (Aug. 4, 1993) at p. 1.)
To avoid harm in existing cases, application of the exclusionary rule could be applied only prospectively. (See Conservatorship of Roulet, supra, 23 Cal.3d at p. 235, fn. 18 [heightened burden of proof applied prospectively].)