They tried to get him into police car for 10min and he resisted, and was saying that he couldn't breathe even prior to the knee+neck incident.
Combine this anecdotal information with a long rap sheet involving felony drug charges ( https://i.redd.it/2sc99kysho151.jpg ) and you have a pretty decent rough estimate that he was on drugs at the time. I'd also like to see official toxicology reports though.