police shoot outs, and a truth revealing video.

I agree with you southland, but I am asking a different question. Why is "eyewitness" evidence - in this case from a camera, only discredited by cops when it is to their advantage? You are a cop, so you know very well that a lot of cases the police put forth depend on eyewitness testimony - testimony from a particular person, from a particular perspective and with all the biases, bad angles, bad lighting, etc. that goes along with it.
I have never seen a cop question eyewitness testimony when it suits their view, only when it hurts them directly or when it hurts their case. And many cases are built entirely on eyewitnesses.