Some prosecutors are trying to fight the opioid epidemic with homicide-related charges against drug dealers in cases involving overdoses, The New York Times reports.

These cases are difficult, prosecutors told the newspaper. They must use toxicology reports to tie medical evidence about the drugs to the fatal overdose. They also have to present evidence that a dealer knew the drugs’ risks but provided them anyway, which is hard to prove. Dealers’ lawyers argue their clients want to keep customers alive because it is good for business.

Juries in these cases must determine whether drug dealers are predators or are addicted to drugs themselves. They also must decide if a dealer should be held responsible for the death of a person who took drugs they knew were dangerous.