Chief,
You have some good points here, but I do have to respond to your inference that officers are looking to charge SOMEONE with a criminal act. That's a little "off-base." When we respond to a shooting scene, we're looking to establish the facts of the incident and to determine in there is criminal liability on the part of any of the parties. That task is facilitated by the availability of information, and is frustrated by the absence of information. Additionally, when officers receive an inbalance of information (one side tells us everything, and the other side remains silent), then there is the risk of an improper conclusion being reached due to the bias of inputs.
I'll bow to you on this, owing to your professional experience. Because I ain't no law enforcement officer, either!
However, I'd like to clarify what I was saying if you don't mind, as it would appear that what I posted was taken to mean the police are looking to charge anybody they can with a criminal act. That was not my intent.
My intent was to emphasize only that the police aren't looking for evidence to establish "innocence". They're looking for evidence that a crime has been committed, and that the evidence will lead them to someone who can be charged and, ultimately, held responsible for it.
"Evidence" being physical, verbal, written, witnessed, etc. And, of course, this starts from the time the police are notified of a particular event and start collecting all this information.
Ideally, the evidence is collected objectively and points towards the "guilty" and away from the "innocent". Or, perhaps in this example, towards "justification" and away from "criminally liable".
But the role of "law enforcement", by definition, does not involve seeking out reasons to declare any given person "innocent", even if the ultimate goal is to find and hold the guilty responsible.
If the evidence says "nothing is here to charge (this person) with (a given crime)", then the investigation looks elsewhere.
By the way...I can only imagine how difficult it is to pursue and properly document, preserve, and maintain the chain of custody for all the different kinds of evidence necessary to successfully legally navigate any criminal investigation. My hat's off to those who can not only do this, but do it well.