Where do you kids get this laced marijuana I hear about? I've spent well over $4,000 on pot in this life life so far and not a dollar of it has been laced. People pay extra for better weed too, if it is higher quality and is from some kind of an established peer "drug dealer" it 99.99% likely isn't laced.
Dried out, compressed and crumbled brick weed seems the most likely candidate as it obviously has been moved the most.