Rubén Zuno Arce, a central defendant in the 1985 torture and killing of an American drug enforcement agent in Mexico, a crime that increased tension between Mexico and the United States in part because of Mr. Zuno’s ties to Mexican government officials, died on Tuesday in a federal prison in Coleman, Fla. He was 82.

The cause was metastatic lung cancer and cardiovascular disease, said Mike Hensley, director of operations for Florida’s District 5 Medical Examiner’s Office.

Mr. Zuno had connections high in the Mexican government and was the brother-in-law of Luis Echeverría Álvarez, who was president from 1970 to 1976. In 1992, he was convicted of kidnapping and conspiracy in the death of Enrique Camarena Salazar, a longtime agent for the United States Drug Enforcement Administration who had helped discover and destroy billions of dollars worth of drugs controlled by the so-called Guadalajara Cartel in the mid-1980s.

The drug gang eventually traced the drug seizures back to Mr. Camarena. On Feb. 7, 1985, they abducted him and his pilot, Alfredo Zavala Avelar, in Guadalajara, tortured and killed them, and left their bodies in a field in the neighboring state of Michoacán. The bodies were found about a month later. A forensic expert later testified that Mr. Camarena, who was known as Kiki, had died of blows to the face and head by a blunt object, most likely a pipe.