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.

That's why we have an adversarial system of law.