I will offer a little subjective example. Were you to see me when I was actively using [for one period of time anyway], you would have observed me injecting about a gram of NYC heroin in one shot [taken as a 60% half gram]. many of my "buddies" were using more. If one was to follow your line of thought, it would be enough to observe us doing so without the slightest ill effect before doing the same yourself. Of course you would have died the second the plunger was depressed. Is it all so imple?
In any event, "eating rolls" will not lead to respitory depression, coma, and death. how could you even try to use that as an example?
You are right on target that "most people buying so called hard drugs have no idea what they are getting." that is why it is of the utmost importance to ascertain what you are using and then to purify said substance to the highest possible degree. Of course, in reality hardly anyone will ever do that but that does not automatically negate that life saving advice. that also does not apply to an entirely unknown substance that does not exhibit any similarities to the substance it is purported to be. For example, if I was offered "crack" that was purple and had the consistency of "Jello" would it be sufficient to simply observe the effects in my "buddies" before dropping it in the "stem?"
"Lab setting..." You do not need a lab to p[erform a simple Marquis. In fact, most US pharmacies now offer a simple home kit that will guive you a color coded result to make it all so simple.
BudTokem: As for your buddy, it was not heroin, that is certain. As with actual opium, it would melt into a viscous dark brown/black oil and then "run." From your description, it does not sound like any opiate/opioid.