Sovereign immunity is literally derived from the divine right of the King to be immune from prosecution and civil suit. It's an anachronism in the legal field,

Sovereign immunity is literally derived from the divine right of the King to be immune from prosecution and civil suit. It's an anachronism in the legal field, and one that most people don't realize exists, but is responsible for a lot of ills in our criminal justice system. There are two types of sovereign immunity granted to law enforcement and prosecutors today. The first is investigative or "qualified immunity," which is the weaker of the two. This is the type of immunity detectives and police officers have in investigating crimes. Prosecutors can occasionally find themselves subject to the same level of immunity if they direct investigations e.g through specific instructions to county detectives or outright interviewing of witnesses not produced by the police. The doctrine states that you cannot sue a person engaged in investigatory activities on behalf of the state unless you can show first that he or she violated a clearly established Constitutional right. So even if a police officer violates a Constitutional right, it must be clearly established. Some states and circuit courts disagree on what "clearly established" means on a per-right basis, but basically if a police officer busts down your door without a warrant absent exigent circumstances, they've lost their immunity, and you can sue him or her for deprivation of civil rights under 42 U.S.C. § 1983. Short of egregious actions, it's difficult to pierce this shield. Many states even have a "good faith" exception to this rule, where if the police officer was unaware that the right they were violating was clearly established, then qualified immunity applies. Which is a perfect example of the law gone haywire. If ignorance of the law isn't a defense for citizens, why should law enforcement officers be able to use it to claim immunity? The second, and much more powerful, form of sovereign immunity is "judicial immunity." It applies not only to judges, who arguably actually should be immune from threats of prosecution, but also to prosecutors during preparation for grand jury and trial. The truly problematic part is that judicial immunity is absolute. It cannot be pierced for any reason, no matter how egregiously a prosecutor violates your Constitutional rights: hiding exculpatory evidence, deliberately keeping you in prison for long periods to force a plea, etc. Of course there is recourse to the ethics committee of a state. However, in all but the most public and embarrassing cases, state ethics boards are toothless against prosecutors. Usually, a complaint has to be a approved by a regional reviewer, who is tied into the county legal system and has a strong incentive not to aggravate the prosecutor's office. The only saving grace here is the "municipal person" theory. Essentially, if a state governmental agency, such as a county, has a policy or practice that actively encourages or directs its employees, whether investigators or prosecutors, to violate Constitutional rights, then one can sue the municipality which is not protected by investigative or judicial immunity under Section 1983.