Mr. Patterson added that he believed that the effort to find and capture Mr. Caro Quintero “transcends politics.”

The murder of Mr. Camarena remains one of the most significant losses in the history of the D.E.A. It galvanized the Reagan-era war on drugs, leading to the nationwide institution of the “Red Ribbon Week,” an annual drug awareness effort.

Mr. Camarena is still honored regularly at D.E.A. offices across the country, where the horror of the 1985 episode lingers. “The investigation of Kiki Camarena’s death is still an open wound,” said John C. Lawn, who led the agency from 1985 to 1990.

“What is meaningful to D.E.A.,” Mr. Lawn added, “is that Caro is on the loose and has been, and we don’t believe that the Mexican government is doing all they can to find him.”

Mr. Caro Quintero initially evaded the authorities in 1985 with the help of a Mexican federal police officer, who was later charged over his role in the escape. The drug kingpin was released in 2013 after his conviction was overturned by a Mexican federal judge, who ruled that Mr. Caro Quintero should have been tried in state court — not federal court — decades before. He quickly disappeared.

In a letter days after Mr. Caro Quintero’s release, nine previous D.E.A. administrators said it had driven “a spike in the heart of Mexican-American bilateral drug enforcement efforts.” The D.E.A. at the time called it “deeply troubling.”

The release happened even as Justice Department authorities said they had made consistently clear to the Mexican government that they were interested in extraditing Mr. Caro Quintero. Asked Thursday about the status of those extradition conversations, James Walsh, who heads the State Department’s Bureau of International Narcotics and Law Enforcement Affairs, declined to comment.

“Corruption that was endemic in 1985 I believe continues to this day,” Mr. Lawn said of Mexico. “We will get closure when Caro is captured.”