Opinion
SULLIVAN, J.
As a result of wounds received at work in a fight with a co-employee, Halfred C. Mathews died on December 3, 1969. His widow’s [724]*724peition for review of the decision of the Workmen’s Compensation Appeals Board (Board) denying compensation presents to us the deceptively simple question whether Labor Code section 3600, subdivision (g),1 which bars an “initial physical aggressor” from benefits, is consonant with section 21, article XX.of the California Constitution.2 We have concluded that the state Constitution does not prohibit the Legislature from conditioning the right [725]*725to compensation upon the absence of wilful misconduct or other intentional wrongdoing. Consequently, we find that section 3600, subdivision (g), is constitutional and that the Board did not err in failing to award compensation in this case.
The unfortunate facts which gave rise to this proceeding may quickly be summarized. Mathews was employed by Western Contractors, Inc. as a heavy-duty truck driver at the Castaic Dam site in Los Angeles County. On September 30, 1969, Mathews had just stopped his truck at the dam site when he was approached by Marcus Cedillo, who was in charge of directing incoming trucks to appropriate places for unloading. Cedillo told Mathews that his truck was blocking traffic and would have to be moved. Mathews replied with an obscene remark and gesture; Cedillo responded similarly.
Mathews climbed down out of the cab of his truck and began walking toward Cedillo with his fists clenched at his sides. Cedillo, who was shorter and lighter than Mathews, picked up two rocks and began backing away. Both men hesitated, and Cedillo drew a line in the dirt with his foot, warning Mathews not to cross it. This action apparently fueled Mathews’ anger. He crossed the line and advanced toward Cedillo. Cedilk> threw one rock past Mathews, who ducked, lost his hard hat, and lunged toward Cedillo to grab or strike him. Cedillo struck Mathews in the forehead with the second rock; Mathews fell and lay unconscious.
As a result of the injuries thus received, Mathews died two months later without ever having regained consciousness. His widow, Jessie Mathews (applicant), sought workmen’s compensation death benefits.
After holding a hearing at which the foregoing evidence was adduced and legal argument was presented, the referee determined that “[t]he evidence leads to the inescapable conclusion that Halfred C. Mathews was involved in an altercation on September 30, 1969, in which he was the initial aggressor.” Nevertheless, the referee awarded full death benefits, holding section 3600, subdivision (g), unconstitutional because it denied “compensation on the basis of the fault of the injured employee.”
Upon reconsideration, the Board found that the injury fell within the terms of section 3600, subdivision (g). However, it held that the section was constitutional and ordered that “applicant take nothing.”
Applicant petitioned for a writ of review annulling this decision. She contends that the Board erred in finding that her husband was the initial physical aggressor in the altercation which caused his death. She also argues that even if the Board’s finding is proper, she is entitled to compensation because section 3600, subdivision (g), is unconstitutional.
[726]*726Section 3600, subdivision (g), bars recovery only when two conditions are present. First, the injury for which workmen’s compensation is sought must “arise out of an altercation.” Second, the injured employee must be the “initial physical aggressor” in that altercation. Section 3202 enjoins us to construe the workmen’s compensation provisions of the Labor Code liberally “with the purpose of extending their benefits for the protection of persons injured in the course of their employment.” Consequently, the provisions of subdivision (g) of section 3600, which deny compensation to persons so injured, must be narrowly and strictly construed. (See Fruehauf Corp. v. Workmen's Comp. App. Bd. (1968) 68 Cal.2d 569, 577 [68 Cal.Rptr. 164, 440 P.2d 236].)
To “arise out of an altercation,” as required by section 3600, subdivision (g), an injury must result from an exchange between two or more persons characterized by an atmosphere of animosity and a willingness to inflict bodily harm. An altercation is distinguishable from “horseplay” or “skylarking,” neither of which involves such animosity, although either may result in bodily harm. (Litzmann v. Workmen's Comp. App. Bd. (1968) 266 Cal.App.2d 203, 209-210 [71 Cal.Rptr. 731]; Argonaut Ins. Co. v. Workmen's Comp. App. Bd. (Helm) (1967) 247 Cal.App.2d 669, 682-683 [55 Cal.Rptr. 810].)
In this case, the record contains ample evidence to support the Board’s finding that Mathews’ injuries arose out of an altercation. It clearly appears that Cedillo and Mathews were not engaged in a joint frolic. On the contrary, each obviously intended to inflict physical harm upon the other; Cedillo was successful. Mathews’ death followed from the injury thus sustained.
The second condition of section 3600, subdivision (g), presents more difficulty; it requires us to determine what type of conduct the Legislature intended to discourage when it denied compensation to an “initial physical aggressor.” As Larson has pointed out, one of the practical difficulties in attempting to bar an aggressor from benefits is “the homely fact that, long after a quarrel is over, it is often almost impossible to determine who really started it.”3 (1 Larson, Workmen’s Compensation Law (1968 ed.) § 11.15(c), p. 159.) Section 3600, subdivision (g), “imposes the necessity of selecting one overt act out of a series of hostile verbal, psychological, and physical acts as the one that, for compensation purposes, caused the quarrel and elicited the ultimate injury.” (Id.)
The Legislature’s use of the word “physical” indicates that it was pri[727]*727marily concerned with the increased risk of injury which arises when a quarrel moves from an exchange of hostile words and nonviolent gestures to a trading of physical blows. Thus, one is not an “initial physical aggressor” so long as he confines his antagonism to arguments, epithets, obscenities or insults. Instead, an “initial physical aggressor” is one who first engages in physical conduct which a reasonable man would perceive to be a “ ‘real, present and apparent threat of bodily harm. . . .’” (Briglia v. Industrial Accident Commission (1962) 27 Cal.Comp.Cases 217, 218.)4
Although the issue is not free from difficulty, nevertheless the record discloses substantial evidence in support of the Board’s conclusion that Mathews was the initial physical aggressor. In the context of his altercation with Cedillo, Mathews’ conduct in leaving his truck and advancing upon Cedillo with clenched fists held at his sides definitely appeared menacing. Since Mathews was several inches taller and 30 pounds heavier than Cedillo, a reasonable man in Cedillo’s position might have considered Mathews’ acts to be a real, present and apparent threat of bodily harm.
Applicant argues that Mathews could not have been the “initial physical aggressor” because he did not “throw the first punch.” However, the Board has properly held that “[i]t is not necessary that there be a battery before one can be deemed a physical aggressor” (Rosenthal v. Wong (1964) 30 Cal.Comp.Cases 103, 104); “ ‘bodily contact ... is not the significant factor.’ ” (Briglia v. Industrial Accident Commission, supra, 27 Cal.Comp.Cases 217, 218.) He who by physical conduct first places his opponent in reasonable fear of bodily harm is the “initial physical aggressor.” His act need not actually cause physical harm; throwing a punch or shooting a gun is not necessary. Under appropriate circumstances, clenching a fist or aiming a gun may be sufficient to convey a real, present and apparent threat of physical injury.
Applicant also contends that even if Mathews became an “initial physical aggressor” by advancing on Cedillo with clenched fists, Cedillo’s later, unjustified use of excessive force in repelling the attack changed the situation, removing the bar to applicant’s recovery. However, section 3600, subdivision (g), simply does not support applicant’s thesis that [728]*728the label “initial physical aggressor” automatically shifts from one disputant to the other whenever either uses excessive force. Rather the section bars compensation to the “initial physical aggressor,” to him who first introduces an element of physical violence into the confrontation, thus creating the risk of injury. Later acts of his opponent, which unjustifiably increase the level of violence, do not absolve the initial aggressor. Consequently, even if Cedillo used excessive force in repelling Mathews’ attack, Mathews was, and remained, the initial physical aggressor. Under these circumstances, the Board correctly concluded that section 3600, subdivision (g), precludes any award of death benefits to applicant.
Her first argument having failed, applicant next asserts that she is entitled to compensation because section 3600, subdivision (g) is unconstitutional. She points out that section 21, article XX of the California Constitution gives the Legislature power to create a complete system of workmen’s compensation providing benefits “irrespective of the fault of any party.” Applicant argues that “ ‘fault’ connotes volitional as well as negligent activity” and that section 21 prohibits the Legislature from conditioning the right to compensation on the absence of fault. Since section 3600, subdivision (g), denies compensation to those who wilfully create violent confrontations, she contends that it implicitly involves a “fault” criterion prohibited by section 21. In support of her argument, she cites State Comp. Ins. Fund v. Ind. Acc. Com. (Hull) (1952) 38 Cal.2d 659 [242 P.2d 311], in which we abolished the judicially created aggressor defense.
While applicant’s argument has a surface plausibility, an examination of the legislative history behind the workmen’s compensation laws and section 21 of article XX demonstrates that the contention rests upon a basic misconstruction of the Constitution. As the following discussion demonstrates, the use of the phrase “irrespective of the fault of any party” in section 21 was intended only to give the Legislature power to grant benefits unhampered by common law tort concepts of negligence; it has never been construed as prohibiting the Legislature from increasing, decreasing or even eliminating awards based upon the wilful wrongdoing of a party.
At the turn of the last century, a public clamor arose for reform of the laws relating to recovery for injuries received at work. By that time increasing industrialization in the United States had combined with an unfortunate development of common law tort doctrines5 to create [729]*729a large number of industrial injuries for which workmen were denied all recovery. (See 1 Larson, supra, § 5.20, pp. 37-39.) California’s first response to this tide of public opinion was to make the fellow-servant rule and the assumption of risk defense inapplicable in certain types of accidents. (Stats. 1907, ch. 97, pp. 119-120; 2 Hanna, Cal. Law of Employee Injuries and Workmen’s Compensation (2d ed. 1970) § 1.03[3][c], pp. 1-15.)
Such minor revisions, however, proved insufficient. In 1911, California joined a rapidly growing number of states in adopting a true workmen’s compensation act (Stats. 1911, ch. 399, p. 796), based on similar legislation enacted in Germany. (See 2 Hanna, supra, § 1.04, pp. 1-18—1-23; 1 Larson, supra, § 5.10, pp. 33-36.) The California legislation, commonly known as the Roseberry Act, abolished the assumption of risk defense and the fellow-servant rule in cases involving industrial injuries, and greatly modified the contributory negligence defense in such cases. (Stats. 1911, ch. 399, § l,p. 796.)
In addition, the Roseberry Act established a voluntary system of workmen’s compensation. The liability of a participating employer for his employee’s injuries was no longer governed by common law tort doctrines. Rather, the act imposed liability for compensation “without regard to negligence” for injuries accidentally sustained by an employee while “performing service growing out of and incidental to” their employment. (Stats. 1911, ch. 399, § 3, pp. 796-797.)6 However, the employer was [730]*730not liable for compensation if the injury was caused by the employee’s own wilful misconduct. (Id.) Where the injury resulted from the employer’s personal gross negligence, wilful misconduct, or violation of any statute designed for the protection of the employee from bodily injury, the injured employee was permitted to choose between statutory compensation and a common law action for damages. (Id.) Under the voluntary plan, therefore, compensation was available without regard to negligence of either employer or employee, but was still denied to an employee guilty of wilful misconduct.
One month after the Roseberry Act became effective, section 21 of article XX was approved by the voters and added to the Constitution. The new section provided: “The legislature may by appropriate legislation create and enforce a liability on the part of all employers to compensate their employees for any injury incurred by said employees in the course of their employment irrespective of the fault of either party.” (Italics added.)
Because few employers had chosen coverage under the voluntary plan established by the Roseberry Act, in 1913 the Legislature exercised the power conferred upon it by section 21 of article XX and enacted a compulsory scheme of workmen’s compensation. (See 2 Hanna, supra, § 1.04[3], p. 1-23.) Officially titled the “workmen’s compensation, insurance and safety act” (Stats. 1913, ch. 176, § 1, p. 279), the new act was popularly known as the Boynton Act. Aside from changing workmen’s compensation from a voluntary to a compulsory system, the Boynton Act strengthened the powers of the Industrial Accident Commission, extended greater control over compensation insurers, and gave the commission power to prescribe safety regulations for employers.
Section 12 of the Boynton Act7 carried forward the provisions of section [731]*7313 of the Roseberry Act, imposing liability for compensation “without regard to negligence.” An employee injured by his own wilful misconduct was still denied compensation. As under the Roseberry Act, an employee was permitted to choose a damage action rather than statutory benefits if his injuries were caused by the employer’s gross negligence or wilful misconduct, indicating “a wilful disregard of the life, limb, or bodily safety of employees.” In addition, section 12 contained new language precluding from compensation those injured by their own intoxication.
In 1917 the Legislature substantially revised the existing law to meet problems which had arisen under the Boynton Act. The “workmen’s compensation, insurance and safety act of 1917” (Stats, 1917, ch. 586, § 2, p. 833) represented the full evolution of the workmen’s compensation system. The policy behind the statute and its goals were summarized in its first section which has been reproduced in the margin.8
[732]*732Section 6 of the 1917 act9 continued in amended form the provisions of section 12 of the Boynton Act and section 3 of the Roseberry Act. Again liability for compensation was imposed on employers “without regard to negligence.” Nevertheless, the 1917 act continued to deny compensation for injuries resulting from the employee’s own intoxication and, for the first time, also barred statutory benefits where the injury was intentionally self-inflicted. Although an employee’s wilful misconduct no longer totally precluded his recovery, it reduced his award by 50 percent. Similarly, an employee injured by his employer’s serious and wilful misconduct was not permitted a damage action, but his award was increased by 50 percent.
[733]*733The same month that the 1917 act was approved, the Legislature, by joint resolution, recommended to the voters an amendment of section 21 of article XX. The proposed amendment duplicated in large measure section 1 of the 1917 act,10 and was intended to remove all doubts as to the constitutionality of then existing workmen’s compensation laws.11 On November 5, 1918, the amendment was approved by the voters.
[734]*734Section 21 of article XX has not been amended since 1918. Nor have the basic provisions of the workmen’s compensation law been changed in the intervening years. Section 3600 of the Labor Code (see fn. 1, ante), which is the codification of section 6 of the 1917 act, still imposes upon employers liability for compensation “without regard to negligence.” It still denies compensation where the injury was caused by the employee’s intoxication or was intentionally self-inflicted. The only significant change has been the addition, in 1961, of subdivisions (f) and (g) which bar the payment of benefits where the employee has “willfully and deliberately caused his own death” or where the injury arises “out of an altercation in which the injured employee is the initial physical aggressor.”
The history detailed above convincingly demonstrates that the words “irrespective.of the fault of any party” were not inserted in section 21, article XX in order to forbid the Legislature from conditioning compensation on the' absence of intentional wrongdoing. Rather, they were used to enable the'Legislature to approach the problem free from the strictures of the common law. Since the passage of the Roseberry Act in 1911, employers have had to compensate their employees “without regard to negligence.” But at the same time, each successive workmen’s compensation act has denied or reduced benefits where the employee engaged in wilful misconduct. Since 1913, compensation has been denied if a workman’s injury resulted from his intoxication, and since 1917 if it was intentionally self-inflicted. Subdivisions (f) and (g), added in 1961, merely continue the pattern of excluding from coverage employees injured by their own intentional wrongdoing. It would be startling, indeed, if we were now to hold that each of these workmen’s compensation acts was unconstitutional" because it conditioned the right to compensation on the absence of intentional misconduct.
Furthermore, our examination of the history behind section 21, article XX indicates that the section was added to the Constitution and then amended for; the sole purpose of removing all doubts as to the con[735]*735stitutionality of the then existing workmen’s compensation statutes. (See fn. 11, ante.) Thus, the section cannot be read as invalidating basic features of those laws as they have existed since 1911. (See Coats, Liability for Fault (1967) 42 State Bar J. 534.)
In sum, the phrase “irrespective of the fault of any party,” which appears in section 21, article XX, must be equated with the phrase “without regard to negligence,” which appears in section 3600. The Legislature quite obviously felt that “fault” and “negligence” were equivalent. From the Roseberry Act until the present day, each statute has imposed liability “without regard to negligence,” while for virtually all of that period the Constitution has contained the phrase “irrespective of the fault of any party.” Indeed, in the 1917 act both phrases were used in the same act —the “fault” language in section 1 (see fn. 8, ante) which states the purposes of the act, and the “negligence” language in section 6 (see fn. 9, ante) which lies at the core of the substantive provisions. When in the same year, 1917, the Legislature recommended the 1918 amendment to section 21, article XX, it likewise used the phrase “irrespective of the fault of any party” to mean that liability could be imposed without regard to negligence. “Irrespective of fault,” just as “without regard to negligence,” was used as a key phrase to indicate that compensation would no longer be ruled by common law tort doctrines. Both phrases became associated with workmen’s compensation in much the same manner as “no-fault” has become attached to a broad range of recent proposed revisions of tort law relating to automobile accidents.
Finally, to hold that section 21 of article XX prohibits the Legislature from taking into account the intentional wrongdoing of employer or employee in providing for compensation would cast doubt over a vast number of other Labor Code provisions which incorporate a notion of intentional fault. If subdivision (g) of section 3600 were to fall, so also should subdivisions (d), (e), and (f), which deny compensation where the injury is caused by intoxication, is wilfully self-inflicted, or is the product of “a deliberate and wilful act of suicide.” Similarly vulnerable would be section 4551, which reduces the award by one-half in most cases in which the injury results from the employee’s serious and wilful misconduct, and section 4553, which increases the award by one-half where the injury is caused by the employer’s serious and wilful misconduct. Doubt would also be cast upon section 4554, which augments the award by 10 percent where the employer wilfully fails to secure payment of compensation; section 4555, which permits an additional award of attorneys’ fees under such circumstances; and section 4557, which increases compensation by 50 percent if the injured employee is under 16 years of age and illegally [736]*736employed at the time of the injury. Other provisions adjusting the award according to the intentional fault of the parties are sections 4053, 4054, 4056, 5705, subdivisions (d) and (e), and 5814. (See generally, Coats, supra, 42 State Bar J. 534.) We do not find that section 21 of article XX requires any such wholesale butchery of the existing workmen’s compensation law.
Contrary to applicant’s assertion, our decision in State Comp. Ins. Fund v. Ind. Acc. Com. (Hull), supra, 38 Cal.2d 659 does not compel the result for which she here contends. While certain broad language in that opinion12 might be construed as intimating that section 21, article XX forbids the legislative enactment of an aggressor defense, such language was unnecessary to- the opinion, and does not represent the considered view of this court on the subject.
In Hull we were concerned only with the judicially created aggressor defense which had evolved in the absence of a specific legislative directive. That judicial doctrine had relied upon the reasoning that by entering into an altercation, the aggressor was departing from his work duties and satis[737]*737fying a personal desire. Therefore, any injuries received during the altercation were said not to “arise out of and in the course of employment.”
In Hull, we rejected this reasoning, recognizing “ ‘that work places men under strains and fatigue from human and mechanical impacts, creating frictions which explode in myriads of ways, only some of which are immediately relevant to their tasks. Personal animosities are created by working together on the assembly or in traffic. Others initiated outside the job are magnified to the breaking point by its compelled contacts. No worker is immune to these pressures and impacts upon temperament. They accumulate and explode over incidents trivial and important, personal and official. But the explosion point is merely the culmination of the antecedent pressures. That it is not relevant to the immediate task, involves a lapse from duty, or contains an element of volition or illegality does not disconnect it from them nor nullify their causal effect in producing its injurious consequences.’” (Original italics.) (38 Cal.2d 659, 666; quoting Hartford Accident & Indemnity Co. v. Cardillo (1940) 112 F.2d 11, 17 [72 App.D.C. 52], cert. den. (1940) 310 U.S. 649 [84 L.Ed. 1415, 60 S.Ct. 1100].)
Pointing out that the Legislature had provided compensation despite contributory negligence and assumption of risk, and had only reduced the award by 50 percent where the injured employee engaged in wilful misconduct, we found no basis for inferring that the Legislature had intended to deny compensation to aggressors. Instead, injuries resulting from altercations clearly fell within the general provisions allowing awards for injuries arising out of and in the course of employment. Since we found that the Legislature intended to allow aggressors to recover, there was no justification for the judicial doctrine precluding an award in such circumstances.
In Hull we held it improper for the judiciary to supplement the workmen’s compensation scheme established by the Legislature. Since Hull, the Legislature has expressly provided that initial physical aggressors shall not receive compensation. As in Hull we now follow the expressed intent of the Legislature.
At oral argument applicant for the first time sought to challenge section 3600, subdivision (g) as being in conflict with article I, section 11 of the California Constitution13 in that it prohibits workmen’s compensation benefits to a class of employees without a rational basis. Con[738]*738trary to the contention of the employer and the Board, section 5904,14 which deems waived all objections not raised in the applicant’s petition for reconsideration, does not prevent us from reaching that issue. Constitutional challenges, which are not cognizable by the W.C.A.B., may be brought before the reviewing court. (National A. & C. Ins. Co. v. Ind. Acc. Com. (Lonnon) (1949) 95 Cal.App.2d 10, 16 [212 P.2d 1]; 1 Hanna, supra, § 10.08[6], p. 10-41.)
Applicant’s point is that enrollees in economic opportunity programs (§ 4207)15 and disaster service workers (§ 4353)16 are not specifically barred from workmen’s compensation recovery when they are the initial physical aggressors, whereas employees are generally so barred under section 3600, subdivision (g). But the Constitution does not require uniform treatment, only a reasonable basis for legislative classification. (Bilyeu v. State Employees' Retirement System (1962) 58 Cal.2d 618, 623 [24 Cal.Rptr. 562, 375 P.2d 442].) It is the duty of the Legislature to determine whether the facts justify such a classification and the burden of the challenger to show that the legislative conclusion is arbitrary. (Professional Fire Fighters, Inc. v. City of Los Angeles (1963) 60 Cal.2d 276, 288-289 [32 Cal.Rptr. 830, 384 P.2d 158].) As we said in Sacramento M. U. Dist. v. P. G. & E. Co. (1942) 20 Cal.2d 684, [739]*739693 [128 P.2d 529]: “Wide discretion is vested in the Legislature in making the classification and every presumption is in favor of the validity of the statute; the decision of the Legislature as to what is a sufficient distinction to warrant the classification will not be overthrown by the courts unless it is palpably arbitrary and beyond rational doubt erroneous. [Citations.] A distinction in legislation is not arbitrary if any set of facts reasonably can be conceived that would sustain it.” We presume the legislative classification is valid and will sustain it “unless it is manifestly without support in reason.” (Western Indemnity Co. v. Pillsbury, supra, 170 Cal. 686, 702 [151 P. 398].)
Generally speaking, an “ ‘[e]mployee’ means every person in the service of an eipployer under any appointment or contract of hire or apprenticeship, express or implied, oral or written, whether lawfully or unlawfully employed . . . .” (§ 3351.) However, the Legislature has excluded certain classes of persons from coverage under the Workmen’s Compensation Act (§ 3352), and it has long been settled that such exclusions do not “make the law vulnerable as special legislation . . . provided the classification be based on some rational ground of differentiation.” (Western Indemnity Co. v. Pillsbury, supra, 170 Cal. 686, 702.) By the same token, extending the coverage of the act to persons not within the definition of “employee,” on terms different from those generally provided, does not violate the prohibitions of our Constitution if a reasonable basis for the distinctions may be found.
In 1946 the Legislature provided in chapter 10 of part 1 of division 4 of the Labor Code (Workmen’s Compensation and Insurance) for the furnishing of compensation to disaster service workers and their dependents for injury or death “within or without the State arising out of and occurring in the course of his activities as a disaster service worker” (§ 4353, italics added). In 1965, the Legislature provided in chapter 9 for the furnishing of compensation to enrollees in economic opportunity programs and their dependents for injury or death “suffered within or without the state occurring in the course of his duties for a sponsoring agency within an economic opportunity program . . . .” (§4207.) In each instance the furnishing of compensation depends upon the concurrence of specified conditions which, except for an additional condition for disaster service workers (see § 4353, subd. (b); see fns. 15 and 16, ante), are substantially the same but are themselves, as applicant points out, in some respects different from the conditions for furnishing compensation to employees generally. It is obvious that these two groups—disaster service workers and enrollees in economic opportunity programs17—do not totally or clearly fit under the [740]*740foregoing definition of “employee” and that a great portion, if not all, of their members might be excluded from the Workmen’s Compensation Act if special provision had not been made for them. We think it clear that the Legislature might have recognized this difference and might have reasonably found that these two groups did not fall within the customary category of employees or at least that the conditions under which they performed their duties were so far different from those involved in the normal employer-employee relationship as to justify different conditions for furnishing compensation.18
Upon an examination of the entire legislative scheme, therefore, we cannot say that these two separate classifications are arbitrary.
We, therefore, conclude that section 3600, subdivision (g) is constitutional, and that the Board did not err in concluding that it precludes an award of workmen’s compensation benefits in this case.
The decision of the Board following reconsideration is affirmed.
Wright, C. J., McComb, J., Tobriner, J., and Burke, J., concurred.