Unfortunately you've confused sovereign immunity for qualified immunity. Try this link instead!
http://dictionary.findlaw.com/definition/immunity.html
Not sure what I've confused, the point made at the link I posted is that immunity was not in the Constitution to begin with and has been expanded to cover more actors since it's inception.
I would add though that in my opinion if any Gov. agents deserve any type of immunity it would be LEO's, by the nature of what they do they have to make split second decisions which could be life or death. Judges, prosecutors, and other state actors do not.