The case is believed to be the first criminal prosecution related to a death caused by the synthetic drug protonitazene in the U.S.

Protonitazene, a synthetic opioid three times stronger than fentanyl, was connected to an overdose in Stevenson Ranch. Dealer knew his pills had killed, but kept dealing anyway.

The U.S. Department of Justice's Los Angeles office filed charges in California in what could be the nation's first death-resulting criminal case involving protonitazene, a synthetic opioid that prosecutors say is "up to three times more powerful than fentanyl.

A Santa Clarita man has pleaded not guilty to a federal charge in what is considered the nation’s first criminal case involving a death caused by the synthetic opioid protonitazene.