What is the design immunity defense?

The "Design Immunity" defense (Gov.Code, 830.6) is raised on a motion for summary judgment, nonsuit, and directed verdict. On submitting such matter, the trial court is invited to rule whether the evidence is sufficient to support the design immunity defense, and if the trial court determines that the defense has been established, the jury is instructed that the public entity is immune as a matter of law for design related damages. (Mozzetti v. City of Brisbane (1977) 67 Cal.App.3d 565, 136 Cal.Rptr. 751.) For reasons stated below, we hold that there was sufficient evidence to support its design immunity defense.