What is the test for reasonable use of deadly force by a police officer?

"The reasonableness of the use of force is evaluated under an 'objective' inquiry that pays 'careful attention to the facts and circumstances of each particular case.' [Citation.] And '[t]he "reasonableness" of a particular use of force must be judged from the perspective of a reasonable officer on the scene, rather than with the 20/20 vision of hindsight.' [Citation.] 'Excessive force claims . . . are evaluated for objective reasonableness based upon the information the officers had when the conduct occurred.' [Citation.]" (County of Los Angeles v. Mendez (2017) ___ U.S. ___, ___ [137 S.Ct. 1539, 1546-1547.)

In the Fourth Amendment context, deadly force is force that creates a substantial risk of death or serious bodily injury. (Smith v. City of Hemet (9th Cir. 2005) 394 F.3d 689, 704-707 and cases cited.) "A police officer's use of deadly force is reasonable if '"'the officer has probable cause to believe that the suspect poses a significant threat of

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death or serious physical injury to the officer or others.' [Citations.]" [Citation.]' [Citation.]" (Brown v. Ransweiler (2009) 171 Cal.App.4th 516, 528.) We may assume, without deciding, that on these facts, the use of deadly force would have been unjustified (or, at least, that a jury could have found it unjustified).