Why drug toxicology tests pm PSH are "inconclusive".
People develop tolerances to heroin, and a lethal dose shifts with time. Many addicts die after getting out of, say 60 or 90 days in jail and detoxing, then coming out and taking the same dose they were before they went in.
Since no one knows how much he was taking before he died, no one can tell what a fatal dose would be.
Hence, "inconclusive".