There isn't heroin in your marijuana... nor is there crystal in your marijuana ... if there was/is, then you would be paying MUCH higher prices - a single joint would cost about $20 more... furthermore, both HEROIN and METHAMPHETAMINE don't smoke good when a direct flame is applied - you need to evaporate them (ie hold the flame under a piece of foil) .. so if you laced a joint with either it would simply burn up, the high would be almost non-existant ...
Dealers don't lace a cheap drug with an expensive drug... the amount of heroin you would put into a single joint is worth much more when sold as HEROIN ...
It's possible, hell, it's possible your joint could be laced with anthrax - but it's not probable...
The only drug you see people lacing marijuanawith is PCP, and it's not like the dealer does this to surprise you - people PAY MORE for the drug...
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"I am not one of those weak-spirited, sappy Americans who want to be liked by all the people around them. I don't care if people hate my guts; I assume most of them do. The important question is: 'What are they in a position to do about it?'" (William S. Burroughs)