A former Border Patrol agent pleaded guilty Thursday in San Diego federal court to a conspiracy charge stemming from his role in a drug-trafficking ring that sent an illegal chemical used to make fentanyl from China to San Ysidro to Mexico.

Cesar Daleo, 47, was arrested last August while driving toward Tijuana. He had with him a package sent from China that he’d just picked up at a San Ysidro post office box, believing it contained 4ANPP, a chemical precursor to fentanyl, federal prosecutors said.

Daleo, who was also indicted in April on federal charges of smuggling protected sea cucumbers and sea horses, worked as a Border Patrol agent in the San Diego area from 1992 to 2003. A resident of San Ysidro, Daleo was living in a Mexican condo at the time of his arrest, prosecutors said.

He pleaded guilty to one count of conspiracy to distribute controlled substances, according to the U.S. Attorney’s Office. He’s scheduled to be sentenced in September by U.S. District Judge Gonzalo Curiel.


The conspiracy charge carries a maximum penalty of 20 years in prison and a $500,000 fine. A plea agreement in the case remained sealed Thursday.

According to federal prosecutors, Daleo picked up at least 13 packages at the San Ysidro post office box before the one he was caught with Aug. 29, while heading south on Interstate 5 toward Tijuana. But the package he had that day was not actually the fentanyl precursor — federal agents had already replaced the chemical with a harmless substitute.

On Aug. 11, a Customs and Border Protection agent at Los Angeles International Airport discovered that the package sent from China and bound for San Ysidro contained 1 kilogram of 4ANPP, which is enough to make 25 kilograms of fentanyl. The chemical was hidden inside a package for lotus root starch, prosecutors said.

Weeks later, with the substitute substance in place, the package was forwarded to San Ysidro, where DEA and other federal agents waited to see who would pick up the shipment. Though the post office box was registered to another man, it was Daleo who picked up the package and signed for it.


Records showed it was the 14th time since December 2016 that Daleo had signed for a package delivered to the post office box, and that he was the only one to ever pick up a package there.

The federal agents followed Daleo until he drove into a freeway lane that led only to Mexico. That’s where they stopped and arrested him.

Federal officials say trafficking rings like the one Daleo was a part of have created what is essentially a fentanyl pipeline from China to the U.S. that’s connected by an online marketplace on the dark web, where drug purchases can be made with anonymity.


The nature of fentanyl — extremely potent in small doses when pure — makes it ideal to move through the mail, keeping packages small and inconspicuous.

The pipeline also brings the cheap 4ANPP from China to the U.S., then south of the border to Mexican cartel strongholds, where it is cut with other substances. The drugs then head north on well-established trafficking routes.

The fentanyl pipeline funnels 80 percent of the drug through the San Diego border before dispersing throughout the U.S.


Twitter: @Alex_Riggins

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alex.riggins@sduniontribune.com