When are law enforcement justified in shooting a fleeing suspect?

When are law enforcement justified in shooting a fleeing suspect?
Steven Miller Answered August 9, 2018
Hardly ever. The person doing the shooting must be able to articulate an objectively reasonable belief, NOT JUST a subjectively reasonable belief, that the state’s self-defense criteria have been met.
Every government officer has a duty to secure your blessings of liberty.  This includes your right to keep and bear arms. A non-shooter  who is fleeing, is not a threat. Open-carry is a right just like any other Constitutionally guaranteed right. The fleeing non-shooter’s rights are “susceptible to restriction only to prevent grave and immediate injury to interests the state may lawfully protect.”
If everyone were to think like a bully, then we could say that an agitated person with a gun in a holster is an imminent threat to everyone else. It doesn’t matter who he works for.
Examples:
  • US Supreme Court’s John Elk v. US, 177 US 529: “… where the officer is killed in the course of the disorder which naturally accompanies an attempted arrest that is resisted, the law looks with very different eyes upon the transaction, when the officer had the right to make the arrest, from what it does if the officer had no right.  … the facts might show that no offense had been committed.”
  • Housh v. Illinois, 75 Ill 491: “An arrest without warrant … or that fails to allege a crime is without jurisdiction, and one who is being arrested, may resist arrest and break away.  If the arresting officer is killed by one who is so resisting, the killing will be no more than an involuntary manslaughter.”
  • West Virginia v. Gum, 69 SE 463: “What rights then has a citizen in resisting an unlawful arrest?  An arrest without warrant is a trespass, an unlawful assault upon the person, and how far one thus unlawfully assaulted may go in resistance is to be determined, as in other cases of assault…. And the authorities are uniform that where one is about to be unlawfully deprived of his liberty he may resist the aggressions of the offender, whether of a private citizen or a public officer, to the extent of taking the life of the assailant….”
  • Washington State v. Rousseau, 40 Wn.2d at 94:  “It is the law that a person illegally arrested by an officer may resist that arrest, even to the extent of the taking of life, if his own life or any great bodily harm is threatened.”
As for already-arrested escapees who are unarmed — United States Supreme Court TENNESSEE v. GARNER (1985):
“Held: The Tennessee statute is unconstitutional insofar as it authorizes the use of deadly force against, as in this case, an apparently unarmed, nondangerous fleeing suspect; such force may not be used unless necessary to prevent the escape and the officer has probable cause to believe that the suspect poses a significant threat of death or serious physical injury to the officer or others. Pp. 7-22. [471 U.S. 1, 2] ”
just like the other rights that the Supreme Court ruled are “susceptible to restriction only to prevent grave and immediate injury to interests the state may lawfully protect.”
Also see the U.S. Supreme Court in Graham v. Connor, 490 U.S. 386 (1989)
ONLY YOU CAN ERASE THE THIN BLUE LINE 
The lower courts often find that “standby officers” who have an opportunity to intervene to prevent unreasonable use of force can be held liable for their failure to do so.
If you witness police brutality, file a criminal complaint against the good cops who did nothing.  Once you file a criminal complaint, you are protected from retaliation.  ANY police contact after that can be called retaliation, and you can file another complaint (it will not go anywhere, but when the police chief runs for reelection it can be used against him).
Here is a contrary opinion:
An editorial in the New York Times How Cops Get Away With Murder, May 30, 2020, page A26  explains how qualified immunity is used by the courts to deprive victims of police abuse any meaningful civil rights remedy.