In 1986 Congress prescribed a 20-year mandatory minimum sentence for drug distribution when "death or serious bodily injury results from" consumption of the drug. Today the Supreme Court unanimously ruled that the penalty applies only when the drug was a necessary or independently sufficient factor in the injury or death. The justices rejected the government's argument that it's enough for the drug to be a contributing factor.
The case involved an Iowa drug dealer named Marcus Barrage, who sold one gram of heroin to Joshua Banka, "a long-time drug user," on April 14, 2010. Banka injected the heroin during "an extended drug binge" that included several other substances. He died the next day, and his blood tested positive not only for morphine (which is what heroin becomes after injection) but also for oxycodone (Percocet), alprazolam (Xanax), and clonazepam (Klonopin). In other words, Banka had consumed four different drugs that cause respiratory depression, which was what killed him.
A forensic toxcicologist who testified at Barrage's trial "could not say whether Banka would have lived had he not taken the heroin"; instead he concluded that the heroin "was a contributing factor." A medical examiner likewise "described the cause of death as 'mixed drug intoxication,'" with each drug "contributing." The judge told the jury that was enough, and the jury convicted Barrage of supplying a drug that resulted in Banka's death, thereby triggering the 20-year mandatory minimum. The U.S. Court of Appeals for the 8th Circuit upheld the conviction. Overturning that decision, the Supreme Court said the government had to show that the heroin supplied by Barrage was a "but-for cause of death," meaning Banka would not have died had he not injected it.
Any legal theory that holds someone else responsible for the reckless behavior that led to Banka's death seems dubious to me, rather like holding a distiller responsible for the death of a college student who dies after chugging a bottle of whiskey. So it counts as an improvement that the Court has made that sort of case harder to argue. How much harder? According to data from the Drug Abuse Warning Network, the vast majority of "drug-related deaths" involving opiates or opioids also involve one or more other drugs. Justice Antonin Scalia, who wrote the majority opinion in Burrage v. U.S., nevertheless argues that "but-for causation is not nearly the insuperable barrier the Government makes it out to be." He cites a couple of cases where the prosecution managed to prove that a given drug was a necessary factor in a user's death even though it was not the only substance consumed. But given how common drug combinations are in so-called overdose deaths, today's ruling surely makes imposing the 20-year mandatory minimum considerably more difficult—a development that should be welcomed by critics of draconian drug penalties.
One can imagine situations in which a drug seller might legitimately be held responsible for a customer's death—if he misrepresents the product's potency, for example, or substitutes a more dangerous drug for the one the buyer thinks he is getting. But that sort of thing is much more likely to happen in the black market created by prohibition than in a legal market. When was the last time you bought a bottle of vodka that turned out to be 160 proof instead of 80, or methanol instead of ethanol? The penalty at issue in this case can be seen as a way for drug warriors to deflect responsibility for the hazards they create.