Hi Hypo
if there's coke and meth in his past then they'd be a major factor in his heart health too, but thats off the topic a little.
I'm not sure a drug test would be proof either way. I have musician acquaintances who don't smoke a few days before a work drug test and pass.
If it was positive he'd probably claim second hand smoke.
I'm sorry but if you're not sure you can trust him the answer is usually no?
D