Forgive me if this is a dumb question, since I'm not that well educated about this. Why can't they sue the police department or some similar body instead of the

Forgive me if this is a dumb question, since I'm not that well educated about this. Why can't they sue the police department or some similar body instead of the individuals? My understanding is that QI protects the individuals, but not the government itself from being sued; however, I don't see any discussion of that route when this defense is brought up.