Even at that, it was not the 'chokehold' that killed Eric Garner. It was being placed on his stomach, with his arms behind his back. It's difficult for anyone to breathe in that position, and _very_ difficult for someone of Eric Garner's size.
Do we actually know whether that was the case? It seems like he might just died from a stress induced heart attack. The preliminary report said that he died of cardiac arrest in the ambulance. I never was able to find a full copy of the final medical examiner report. The summary of the final report was that he basically died of everything, which was not at all helpful.