Sovereign immunity is a complex topic and manifests itself in various ways in various circumstances. A comprehensive discussion of sovereign immunity in the United States is well beyond the scope of this thread. If anyone is interested in beginning his (or her) study of the principle, here are links to a couple of articles that might help start him (or her) on the way:
"Suing the Federal Government"; and
"A Primer on the Doctrine of Federal Sovereign Immunity".
Second, the principle of sovereign immunity does not foreclose suing the government to challenge the validity or application of a law.
Third, we're here discussing primarily 42 USC 1983, a federal law that under certain circumstances allows suits for damages against government officials (thus limiting sovereign immunity). Other laws or judicial decisions might limit sovereign immunity (e. g., the Federal Tort Claims Act) in other circumstances, but discussion of those laws in also outside the scope of this thread.
But to return to the subject matter of this thread, the law being discussed, 42 USC 1983, is an example of a conscious erosion by government of sovereign immunity. Again, 42 USC 1983 provides:
Every person who, under color of any statute, ordinance, regulation, custom, or usage, of any State or Territory or the District of Columbia, subjects, or causes to be subjected, any citizen of the United States or other person within the jurisdiction thereof to the deprivation of any rights, privileges, or immunities secured by the Constitution and laws, shall be liable to the party injured in an action at law, suit in equity, or other proper proceeding for redress, ...
By expressly permitting suits against government personnel when their conduct amounts to a "deprivation of any rights, privileges, or immunities secured by the Constitution and laws", the statute effectively waives sovereign immunity with respect to that sort of misconduct. And in that way government officials are held accountable for their misdeeds if they deprive one of "any rights, privileges, or immunities secured by the Constitution and laws."
The case law defining Qualified Immunity under 42 USC 1983 is really about defining what conduct is or is not permissible under the Constitution. It is not about escaping liability for wrongful acts. It's about defining when conduct is wrongful and when it is not.
So let's look at a couple of examples of the application of qualified immunity principles in a 42 USC 1983 action against an LEO based on alleged excessive force. In the cases cited the application of qualified immunity is related to the question of the reasonableness of the LEO's use of force and the necessity of that force in light of a manifest lethal threat to either the officer or others.
So, for example, in
Tennessee v. Garner, 471 U.S. 1, 105 S.Ct. 1694, 85 L.Ed.2d 1 (1985), the Supreme Court rejected a claim of qualified immunity noting (at 20-21):
....In reversing, the Court of Appeals accepted the District Court's factual conclusions and held that "the facts, as found, did not justify the use of deadly force." 710 F.2d, at 246. We agree. Officer Hymon could not reasonably have believed that Garner—young, slight, and unarmed—posed any threat. Indeed, Hymon never attempted to justify his actions on any basis other than the need to prevent an escape. The District Court stated in passing that "[t]he facts of this case did not indicate to Officer Hymon that Garner was 'non-dangerous.' " App. to Pet. for Cert. A34. This conclusion is not explained, and seems to be based solely on the fact that Garner had broken into a house at night. However, the fact that Garner was a suspected burglar could not, without regard to the other circumstances, automatically justify the use of deadly force. Hymon did not have probable cause to believe that Garner, whom he correctly believed to be unarmed, posed any physical danger to himself or others....
On the other hand, in
Mullenix v. Luna, 136 S. Ct. 305, 193 L. Ed. 2d 255 (2015), the Supreme Court in finding qualified immunity noted (135 S. Ct., at 310):
....This Court has considered excessive force claims in connection with high-speed chases on only two occasions since Brosseau . In Scott v. Harris, 550 U.S. 372, 127 S.Ct. 1769, the Court held that an officer did not violate the Fourth Amendment by ramming the car of a fugitive whose reckless driving "posed an actual and imminent threat to the lives of any pedestrians who might have been present, to other civilian motorists, and to the officers involved in the chase." Id., at 384, 127 S.Ct. 1769. And in Plumhoff v. Rickard, 572 U.S. ––––, 134 S.Ct. 2012, 188 L.Ed.2d 1056 (2014), the Court reaffirmed Scott by holding that an officer acted reasonably when he fatally shot a fugitive who was "intent on resuming" a chase that "pose[d] a deadly threat for others on the road." 572 U.S., at ––––, 134 S.Ct., at 2022. ....
So in
Garner the officer was not entitled to qualified immunity for his use of lethal force because he had no basis upon to reasonably believe that the subject posed an imminent lethal threat to the officer or others. On the other hand, in
Mullenix the officers involved were entitled to qualified immunity because the use of lethal force could be justified by the actual and imminent danger the subject posed to others.
