How have courts rejected defendants' immunity defense?

We reject defendants' immunity defense for several reasons. First, defendants failed to raise the immunity issue in the trial court, which denied plaintiff the opportunity to either contest the claim or amend the pleading to rebut the defense. The general demurrer did not suffice to raise the immunity defense. (See Color-Vue, Inc. v. Abrams (1996) 44 Cal.App.4th 1599, 1604.) Unlike some other government immunities, the particular immunity granted by section 6736(a), is not jurisdictional, but rather requires an affirmative showing by the defendant of an exception to liability, and thus is forfeited on appeal if not raised by demurrer or as an affirmative defense. (See McMahan's of Santa Monica v. City of Santa Monica (1983) 146 Cal.App.3d 683, 689.)