In Ferrell v. Industrial Commission, 79 Ariz. 278, 280, 288 P.2d 492, 494 (1955), the issue was whether claimant, a volunteer civil defense worker, was an employee of the State within the meaning of the Act. Id. at 279, 288 P.2d at 493. The relevant portion of the statute, which is now A.R.S. 23-901(6)(a), defined "employee" to include, "every person in the service of the state or of a county, city, town, municipal corporation or school district, including regular members of lawfully constituted police and fire departments of cities and towns, whether under election, appointment or contract of hire." Id. at 280, 288 P.2d at 494. Although the initial phrase, "every person in the service of the state," could by its terms include a volunteer, the court found limits implicit in the remainder of the definition, "including regular members of lawfully constituted police and fire departments of cities and towns, whether under election, appointment or contract of hire." Id. at 280-81, 288 P.2d at 494. The court held that claimant was not a "person in the service of the state," noting the absence of any reference to "volunteer workers" connotes "a legal duty to do the acts being performed when ... injured" and reasoning that the phrase "contract of hire" requires "payment of some kind." Id. Further, the court applied the expressio unius rule to reject the argument that the claimant should be included in the definition of "employee" based on another provision specifically including volunteer firemen. Id. at 281-82, 288 P.2d at 494-95. The court explained: "The fact that the legislature saw fit specifically to include volunteer firemen within the limits of the Act would seem to indicate, under the expressio unius rule, that the legislative intent was to exclude other groups wherein no contract contemplating payment of wages existed." Id.