An underground economy which people defend by killing, which people encroach on by killing. People rip each other off because they know the other party, most likely, will not go to the cops, and can't seek justice through the court system, so those disputes are "solved" by violence too.
Surely more people have died in turf battles than due to shooting up some unknown substance of unknown quality; both problems solved by ending the Drug War.
This is a great handout to give to the police you see. Tell them their lives are worth more than a bag of marijuana or cocaine or heroin or meth.
This handout can also be effective in areas plagued by gang violence. But most everyone will be able to understand the logic of this one.