If drugs were legal, and the invested reputations of branded resalers and manufacturers were on the line with each transaction, this sort of thing could hardly happen:

At least 12 people in Wayne County have died in two days from a lethal dose of heroin and cocaine mixed with a pain control drug, officials said today.

And in the event that it did, the producers could be held liable for the crimes. That they might be held liable is sufficient incentive to avoid such dilution and debasement of their product.

Currently, there is no such liability, and hence no such accountability on behalf of the vendors of such products. The results are not unexpected.