Immunity creep

It is a long-established doctrine of law that officials should not be subject to civil or criminal prosecution for acting within their jurisdiction, and constitutions and laws sometimes make that official immunity explicit. However, over time judges have been extending that immunity from momentary actions to everything done "on duty" or perhaps even "while in office". The practical effect of this is to convert official titles into "titles of nobility", putting officials beyond the law or accountability for their misconduct. Removal from office can be a remedy, but too much misconduct needs other remedies, and we are headed for a clash in which the public will demand them.

For more on this see

Immunity - Official Immunity
Qualified immunity — Wikipedia
Defenses: Official Immunity
Supreme Court Case Establishes Official Immunity for Police Officers and Police Departments in New Hampshire, by Charles P. Bauer
Defenses: Qualified official immunity
Private-Law Models for Official Immunity, by Richard Epstein
Tort - Defamation - Elected Official Immunity, by Edward Wesoloski
The Case Against Official Immunity, by Jesse Walker
Absolute Immunity on Trial, by Radley Balko
Supreme Court rules witnesses cannot be sued under 1983 for the content of their testimony - Briscoe v. LaHue, 460 U.S. 325 (1983)

The original standard was that while officials might have immunity from judgment, they did not have immunity from prosecution, and that it was for a trial to determine what immunity, if any, the defendant should have.