What is the test for equal protection in the context of an involuntary commitment statute?

Under either a due process or equal protection challenge to an involuntary commitment statute, the principal focus is, as both the district court and the parties recognize, upon the governmental interest at stake. If that interest continues to be substantial, the dictates of equal protection are satisfied even under a heightened scrutiny standard of review. Correspondingly, if a classification passes equal protection muster under heightened scrutiny, then, for purposes of due process, the nature and duration of commitment would necessarily bear a "reasonable relation to the purpose for which the individual is committed." Jackson v. Indiana, 406 U.S. 715, 738, 92 S.Ct. 1845, 1858, 32 L.Ed.2d 435 (1972).