How the Government Deceived Congress in the Debate over Surveillance Powers (2013)
eff.org
eff.org
Here's a 2018 article listing some prosecutions: https://www.nbcnews.com/politics/congress/5-people-who-lied-...
Because it's the DoJ prosecuting, I think it's uncommon for the government to prosecute administration witnesses, even from previous administrations. Once upon a time Congress would prosecute and impose punishment itself: https://en.wikipedia.org/wiki/Contempt_of_Congress#Inherent_...
If you can't (or won't) be prosecuted, why hide your crime?
Meanwhile, the U.S. Supreme Court has ruled that the President is largely immune from prosecution. The width of that decision can be fleshed out by additional court cases if there is anybody with the authority and courage to risk it. The risks are very high and very real. The rewards are debatable.
A simple statement like, "The deceased was an evil threat to the security of America" is enough to put any prosecution way out on a limb. Look how hard it is to get justice in Minneapolis. Things are very murky. And that didn't involve the President being the gunman.
Unfortunately, the brazen public crimes our president has been committing lately are much more high level. Thousands of innocent lives have been (and will be) ended, usually by much more dramatic and damaging means. The parts of our government that are responsible for prosecuting those crimes have decided to join in instead.