It proves several things. The first is that he was alive. The second is that he was conscious. The third was he was talking. The fourth is that EMS was there in 3 minutes. The fifth is that he was taken from the scene alive and conscious.
Contrary to popular belief and misperception, Mr. Garner was not choked to death, nor was he sat upon for any particular length of time. The preliminary autopsy shows no damage to the windpipe or the muscles of the neck, thus no strangulation. Additionally, asphyxia was not a cause of death.
In short, don’t believe the hype. The man resisted arrest, and because his health conditions, expired. He was not choked, nor strangled. He had an heart attack in the ambulance, was morbidly obese, and suffer chronic asthma. In short, he was a ticking time bomb.
Point being, you give me 1 or 2 seconds to wrap my arm around another man's neck and tighten as hard as I can (as it appears the officer did in the first vid), I could do some lasting damage and death would definitely would not be out of the question. Even if it wasn't instantaneous.
I watch those videos knowing what he was being arrested for and think the whole thing stinks and was a disgrace. I initially thought all the involved cops should be charged. And nothing I've read here has changed that.