The opinion
RICHARDSON, J.
I respectfully dissent. As will appear, I would sustain petitioner’s challenge to the constitutionality of Labor Code section 3212.5 (unless otherwise indicated, all statutory references are to that code).
Generally, under the Workers’ Compensation Act (§ 3201 et seq.) employees do not receive workers’ compensation for injuries which are not “proximately caused by the employment.” (§ 3600, subd. (c).) Thus, disabilities resulting solely from a condition which arises either before or after employment are ordinarily excluded from the application of the act. Section 3212.5, however, provides that for purposes of determining eligibility for workers’ compensation benefits of policemen and other law enforcement officers, any heart trouble or pneumonia suffered by such *120 employees which develops or manifests itself during the course of employment cannot be attributed to any preexisting disease.
The City and County of San Francisco (hereinafter City) challenges section 3212.5 on the ground, among others, that in enacting section 3212.5 the Legislature exceeded the authority conferred upon it by the California Constitution. I agree with City.
Leonard Wiebe was employed by City as a policeman from July 13, 1943, to November 16, 1968, when he retired from the police department. Following his retirement, he worked as a special investigator for the Bank of America (hereinafter Bank) until September 3, 1972, the date of his death. Upon his death, his widow and minor child (hereinafter claimants) applied to respondent board for death benefits and compensation for burial expenses, naming City as defendant and alleging that Wiebe’s death was due to stress and strain arising out of and in the course of his employment with City. At City’s request Bank was subsequently joined as party defendant.
The matter was submitted to the workers’ compensation judge on the basis of stipulations as to the decedent’s employment history and medical evidence consisting solely of a written report and a deposition of Frederic Mintz, M.D., a cardiovascular specialist. According to this medical evidence, Wiebe died of an acute myocardial infarction resulting from coronary atherosclerosis disease, described by Dr. Mintz as a progressive condition generally originating in childhood and well established in most American male victims by the age of 25. Dr. Mintz in his deposition testified that in his opinion, Wiebe’s occupation as a police officer “did not play a role in the progression of this disease.” In his earlier medical report Dr. Mintz had similarly concluded, “I cannot ... on medical grounds reasonably relate his coronary heart disease and myocardial infarction to his employment as a police officer. . . .”
The workers’ compensation judge made findings that decedent sustained an injury to his heart while employed by City and that there was no evidence linking decedent’s death to his employment with Bank. In his report, the judge acknowledged that there was no medical evidence indicating that decedent’s disease was related to his employment as a police officer. Nevertheless, because of the section 3212.5 presumption the judge deemed himself compelled to find that decedent died as a result of a myocardial infarction “. . . which arose out of and occurred in the course and scope of his employment as a police officer for the City and *121 County of San Francisco.” On this basis alone, an award was made to claimants. The findings and award were affirmed by the appeals board, and City has sought our review.
The statute in question, section 3212.5, provides in pertinent part: “In the case of a member of a police department of a city or municipality, . . . the term ‘injury’ as used in this division includes heart trouble and pneumonia which develops or manifests itself during a period while such member,... is in the service of the police department,. . . [¶] Such heart trouble or pneumonia so developing or manifesting itself shall be presumed to arise out of and in the course of the employment; . . . This presumption is disputable and may be controverted by other evidence, but unless so controverted, the appeals board is bound to find in accordance with it. . . . [¶] Such heart trouble ... so developing or manifesting itself in such cases shall in no case be attributed to any disease existing prior to such development or manifestation.” (Italics added.)
As will be seen the effect of section 3212.5 is to create a presumption that heart trouble which develops or manifests itself during performance of the specified work is employment related, a presumption that cannot be rebutted by evidence of any preexisting disease. (Bussa v. Workmen’s Comp. App. Bd. (1968) 259 Cal.App.2d 261, 265 [ 66 Cal.Rptr. 204 ]; Turner v. Workmen’s Comp. App. Bd. (1968) 258 Cal.App.2d 442, 449 [ 65 Cal.Rptr. 825 ]; Ferris v. Industrial Acc. Com. (1965) 237 Cal.App.2d 427, 431-433 [ 46 Cal.Rptr. 913 ].) The only recognized exception to the foregoing presumption arises in those cases in which a prior disease is evaluated in connection with a worker’s previous compensation claim. In such instances the disability can be apportioned to the prior disease. (E.g., State Comp. Ins. Fund v. Industrial Acc. Com. (Quick) (1961) 56 Cal.2d 681 [ 16 Cal.Rptr. 359 , 365 P.2d 415 ].) In the absence of any such overlapping disabilities, however, the statutory liability of employers is not affected by evidence that the employee’s heart disease may have been causally related to a disease which preexisted the employment.
The constitutional and statutory origins of California’s workers’ compensation may be briefly examined.
Article XIV, section 4, of the California Constitution provides: “The Legislature is hereby expressly vested with plenary power, ... to create, and enforce a complete system of workers’ compensation, by appropriate legislation, and in that behalf to create and enforce a liability on the part *122 of any or all persons to compensate any or all of their workers for injuiy or disability, and their dependents for death incurred or sustained by the said workers in the course of their employment, irrespective of the fault of any party.” (Italics added.) City argues that in enacting section 3212.5 the Legislature impermissibly exceeded its foregoing constitutional grant of authority and, for reasons which I develop below, I agree.
Pursuant to article XIV, section 4, the Legislature enacted section 3600, imposing liability upon the employer for disabilities and death “arising out of and in the course of employment,” and under subdivision (c) of the section, “[w]here the injuiy is proximately caused by the employment . . . .” Only employment related diseases or injuries are covered. It follows that disabilities or death which are wholly traceable to a physical condition that existed prior to employment or arose after employment terminated are excluded from the application of the act. Section 3212.5, however, purports to provide that any heart trouble or pneumonia suffered by designated public employees (police and other law enforcement officers), which develops or manifests itself during the course of employment, cannot be attributed to any preexisting disease. In effect, the Legislature has imposed upon public employers workers’ compensation liability for a police officer’s heart trouble, even though a preexisting disease may have been the sole cause of the disability. I conclude that the Legislature lacks the constitutional power to do this.
As previously noted, the only medical evidence in the record before us is the testimony of Dr. Mintz to the effect that the fatal heart attack was the result of atherosclerosis, and was in no way a consequence of, or related to, Wiebe’s career as a peace officer for City. The Wiebes presented no contrary medical testimony. Accordingly, the record, as it relates to medical causation, discloses unequivocally, and beyond challenge, that the heart condition in question was neither caused nor aggravated by the deceased’s city employment, but resulted solely from an earlier developmental condition. Section 3212.5, however, conclusively presumes that Wiebe’s death could not have been caused by the earlier condition. Reduced to its barest formulation, the case before us assumes this posture—from the record, what medically was, from the statute, legally cannot be.
The majority urges that the section 3212.5 conclusive presumption is a mere regulation of evidence, a permissible control upon the manner and method of trial. Such is not the case, however, and the effect of the *123 section is not nearly so modest. Although a rebuttable presumption operates only to shift the burden of proof, or to allocate the burden of producing evidence (Evid. Code, § 601), we have held that a conclusive presumption “is in actuality a substantive rule of law.” (Kusior v. Silver (1960) 54 Cal.2d 603, 619 [ 7 Cal.Rptr. 129 , 354 P.2d 657 ]; see Note, Irrebutable Presumptions: An Illusory Analysis (1975) 27 Stan.L.Rev. 449, 462-464; Note, The Irrebuttable Presumption Doctrine in the Supreme Court (1974) 87 Harv.L.Rev. 1534, 1544.) Further, we have said that such a conclusive presumption is valid only to the extent that the Legislature is empowered to achieve by direct legislation the result indirectly accomplished by the presumption. (Kusior, supra, at p. 619 ; see Usery v. Turner Elkhorn Mining Co. (1976) 428 U.S. 1, 23 [ 49 L.Ed.2d 752, 771 , 96 S.Ct. 2882 ].)
In the matter before us, the constitutional directive which simultaneously confers and limits legislative power is very clear and unambiguous. The Legislature may impose workers’ compensation liability for injuries suffered “in the course of. . . employment.” (Cal. Const., art. XIV, § 4, italics added.) We have long held that affirmative grants of constitutional power are exclusive, negating any powers not specifically granted. (Gilgert v. Stockton Port District (1936) 7 Cal.2d 384, 387-389 [ 60 P.2d 847 ]; Martello v. Superior Court (1927) 202 Cal. 400, 404-406 [ 261 P. 476 ]; see also Morse v. Municipal Court (1974) 13 Cal.3d 149, 150 [ 118 Cal.Rptr. 14 , 529 P.2d 46 ].) Where, as here, statutory implementation is permissive rather than mandatory the Legislature may decline to exercise the full scope of its constitutionally conferred authority. (Ruiz v. Industrial Acc. Com. (1955) 45 Cal.2d 409 [ 289 P.2d 229 ].) What it may not do, however, is act beyond the limits of that authority. Unlike a rebuttable presumption, which may result in compensation for nonworkrelated injuries if the employer fails to carry the burden of proof assigned to him, a conclusive presumption, framed as an absolute prohibition against evidence of preexisting disease, necessarily and uniformly achieves the same result as an affirmative legislative command to compensate for disabilities that do not arise out of employment. The creation of a conclusive presumption, clearly and fundamentally, is no less a breach of permissible constitutional boundaries than the more direct statutoiy imperative.
The majority opinion justifies the conclusive presumption of section 3212.5 on the ground of administrative convenience, since it assertedly resolves a “split in medical opinion” regarding the effect of job stress. *124 Under the majority’s analysis, the section merely settles an abstract dispute between “two competing schools of medical thought” regarding job stress. If, indeed, this was the section’s only effect, the majority’s error would not be so serious.
The fact is, however, that section 3212.5 is wholly silent on the controversial issue of job stress. Instead of resolving any medical dispute, the section flatly prohibits the employer from introducing evidence of a preexisting disease which might have caused the present disability. The majority persists in failing to discern that there is no medical dispute whatever on the issue that a preexisting disease can cause heart trouble. (See generally, Lamb v. Workmen’s Comp. Appeals Bd. (1974) 11 Cal.3d 274, 278-279 , 281 & fn. 6 [ 113 Cal.Rptr. 162 , 520 P.2d 978 ]; Saal v. Workmen’s Comp. Appeals Bd. (1975) 50 Cal.App.3d 291, 294 [ 123 Cal.Rptr. 506 ]; Greenberg v. Workmen’s Comp. Appeals Bd. (1974) 37 Cal.App.3d 792, 794-797 [ 112 Cal.Rptr. 626 ]; Fontno v. Workmen’s Comp. App. Bd. (1969) 273 Cal.App.2d 684, 687-688 [ 78 Cal.Rptr. 291 ]; 1A Larson, Workmen’s Compensation Law (1973) § 38.83, pp. 7-197 - 7-198; Note, Workmen’s Compensation—Diseases Arising Out of Employment —A Problem of Proof (1971) 2 Pacific L.J. 678, 688-691.)
Labor Code section 3212.5 is unconstitutional because, flying in the face of indisputable medical evidence, it permits an award of workers’ compensation to an employee whose job may have played no role whatever in causing his disability, contrary to the Legislature’s express constitutional authorization. The Legislature might properly have determined that, despite medical doubt on the subject, job stress can cause heart trouble. What the Legislature cannot do constitutionally is to exclude evidence that, in a particular case, the disability was solely caused by a preexisting disease, rather than by job stress. This is precisely what section 3212.5 purports to provide, as will be observed from a most casual reading of the section.
The majority’s reliance upon Usery v. Turner Elkhorn Mining Co., supra, 428 U.S. 1 , is totally misplaced. Usery upheld legislation prohibiting denial of workers’ disability benefits solely on the basis of a negative X-ray. As the high court explained, the provision was supported by “Congress’ reasoned reservations regarding the reliability of negative X-ray evidence.” (P. 31 [49 L.Ed.2d p. 776], italics added.) No such reasoned doubts exist with respect to the role of preexisting disease in heart disability cases.
*125 In this regard, section 3212.5 not only exceeds the limits of the fundamental constitutional provision from which California’s workers’ compensation arises, but it violates due process as well. Whatever the precise standard may be for testing those conclusive presumptions contained in social welfare or similar statutory schemes (compare, e.g., Vlandis v. Kline (1973) 412 U.S. 441 [ 37 L.Ed.2d 63 , 93 S.Ct. 2230 ], with Weinberger v. Salfi (1975) 422 U.S. 749 [ 45 L.Ed.2d 522 , 95 S.Ct. 2457 ]), the absolute minimum criterion is reasonableness. (Cf. People v. Dubose (1974) 42 Cal.App.3d 847, 850 [ 117 Cal.Rptr. 235 ].) I acknowledge that it is no simple matter to reconcile the commendable broad constitutional requirement, on the one hand, that the workers’ compensation scheme “accomplish substantial justice in all cases expeditiously, inexpensively, and without incumbrance of any character” (Cal. Const., art. XIV, § 4), a not inconsiderable task, with the inherent constitutional limitation of the work-relatedness rule, on the other. Doubtless, to achieve that accommodation, the Legislature may manipulate evidentiary rules to give claimants the benefit of every legal doubt, but it may not, through section 3212.5, award the benefit of a doubt where no doubt exists.
From the foregoing discussion, it will be seen that an attempt to resolve the problem of conflicting medical testimony, as section 3212.5 purports to do, by absolutely and conclusively eliminating any evidence of a nonjob-related factor medically capable of causing the entire damage for which compensation is sought, passes all the bounds of logic, common sense and reason. The Legislature may quite properly demonstrate solicitude for the health and safety of peace officers who daily safeguard the lives of our citizens, often at the risk of their own. Yet, this solicitude must find its proper expression within the bounds of the same Constitution that protects us all. In short, the section 3212.5 prohibition against any evidence of preexisting heart disease is arbitrary, capricious, and operates to deprive public entities, as employers, of a fair opportunity to protect their legitimate interests.
I would annul the decision of the appeals board.
Clark, J., and Manuel, J., concurred.
Petitioner’s application for a rehearing was denied October 20, 1978. Clark, J., Richardson, J., and Manuel, J., were of the opinion that the application should be granted.