Alleged drug cartel boss Rafael Caro Quintero, who spent decades in prison in Mexico for the murder of a U.S. drug enforcement agent, pleaded not guilty in a U.S. court on Friday to drug trafficking charges that could result in his execution.

After years as one of U.S. authorities' most wanted men, Mexican drug cartel boss Rafael Caro Quintero was brought into a New York courtroom Friday to answer charges that include orchestrating the 1985 killing of a U.

Rafael Caro Quintero, nicknamed “El Narco de Narcos” (The Narco of Narcos) is the founder of the now defunct Guadalajara Cartel—one of the most powerful drug cartels of the 1980s that later splintered into various groups, including the Sinaloa Cartel, one of the world’s most powerful criminal organizations and drug cartels.