What is the test for the doctrine of "overbreadth" in the context of First Amendment freedom of expression legislation?

litigants may challenge a statute not because their own rights of free expression are violated, but because the very existence of an overbroad statute may cause others not before the court to refrain from constitutionally protected expression. [Citations.] (In re M.S. (1995) 10 Cal.4th 698, 709, 42 Cal.Rptr.2d 355, 896 P.2d 1365.) To avoid being unconstitutionally overbroad, statutes attempting to restrict or burden the exercise of First Amendment rights must be narrowly drawn and represent a considered legislative judgment that a particular mode of expression has to give way to other compelling needs of society. [Citations.] (Broadrick v. Oklahoma (1973) 413 U.S. 601, 611612, 93 S.Ct. 2908, 37 L.Ed.2d 830.) The overbreadth doctrine is, manifestly, strong medicine which has been used sparingly and only as a last resort. (Id. at p. 613, 93 S.Ct. 2908.)