When the Appeals Board interprets workers’ compensation statutes, its fundamental objective is to determine the Legislature’s intent so as to effectuate the purpose of the law. (DuBois v. Workers’ Comp. Appeals Bd. (1993) 5 Cal.4th 382, 387 [58 Cal.Comp.Cases 286]; Nickelsberg v. Workers’ Comp. Appeals Bd. (1991) 54 Cal.3d 288, 294 [56 Cal.Comp.Cases 476]; Moyer v. Workmen’s Comp. Appeals Bd. (1973) 10 Cal.3d 222, 230 [38 Cal.Comp.Cases 652].)

The best indicator of legislative intent is the clear, unambiguous, and plain meaning of the statutory language. (DuBois v. Workers’ Comp. Appeals Bd., supra, 5 Cal.4th at pp. 387-388; Gaytan v. Workers’ Comp. Appeals Bd. (2003) 109 Cal.App.4th 200, 214 [68 Cal.Comp.Cases 693]; Boehm & Associates v. Workers’ Comp. Appeals Bd. (Lopez) (1999) 76 Cal.App.4th 513, 516 [64 Cal.Comp.Cases 1350].) Thus, in interpreting statutory provisions, we will first look to the express language of the statutes themselves. (DuBois v. Workers’ Comp. Appeals Bd., supra, 5 Cal.4th at p. 387; Moyer v. Workmen’s Comp. Appeals Bd., supra, 10 Cal.3d at p. 230.) When the statutory language is clear and unambiguous, the WCAB will enforce the statute according to its plain terms. (DuBois v. Workers’ Comp. Appeals Bd., supra, 5 Cal.4th at p. 387; Atlantic Richfield Co. v. Workers’ Comp. Appeals Bd. (Arvizu) (1982) 31 Cal.3d 715, 726 [47 Cal.Comp.Cases 500].)

Additionally, however, a statute’s words must be construed in the context both of the entire statute and the entire statutory scheme, so that the language is harmonized both internally and with related statutes, to the extent possible. (Chevron U.S.A., Inc. v. Workers’ Comp. Appeals Bd. (Steele) (1999) 19 Cal.4th 1182, 1194 [64 Cal.Comp.Cases 1]; DuBois v. Workers’ Comp. Appeals Bd., supra, 5 Cal.4th at pp. 387-388; Moyer v. Workmen’s Comp. Appeals Bd., supra, 10 Cal.3d at pp. 230-231; Gee v. Workers’ Compensation Appeals Bd. (2002) 96 Cal.App.4th 1418, 1427 [67 Cal.Comp.Cases 236]; American Psychometric Consultants, Inc. v. Workers’ Comp. Appeals Bd. (Hurtado) (1995) 36 Cal.App.4th 1626, 1639 [60 Cal.Comp.Cases 559].) Further, it is a principle of statutory construction that the word “shall,” as used in the Labor Code, ordinarily connotes a mandatory duty. (Lab. Code, §15 [“‘[s]hall’ is mandatory and ‘may’ is permissive”]; see also, Smith v. Rae-Venter Law Group (2003) 29 Cal.4th 345, 357; Jones v. Tracy School Dist. (1980) 27 Cal.3d 99, 109; Morris v. County of Marin (1977) 18 Cal.3d 901, 907.)

From Willette.