Costa Rica’s chief prosecutor, Carlo Díaz, said Monday he’ll investigate the political ties of Guobin Tam Zhang, a U.S.-wanted drug suspect photographed at President Laura Fernández’s election victory party. Díaz didn’t wait for a complaint. He’s opening the inquiry on his own initiative.
Tam, also known as Juan Carlos Tam Cheong, is a China-born naturalised Costa Rican facing extradition to the United States under a Florida federal indictment alleging drug trafficking and money laundering. Police arrested him near San José three days before Díaz announced the probe.
The Prosecutor’s Mandate
“We are going to investigate any other background or relationship this person has at the political level,” Díaz told La Nación. The inquiry will examine money laundering and possible illegal financing of the last election campaign. First, prosecutors need a report from the party-finance department of the Supreme Electoral Tribunal (TSE), Costa Rica’s election authority.
With a judge’s approval, investigators opened five devices seized from Tam, including four phones. Findings could lead to cases against other people, Díaz said. His office will suspend Tam’s local cases to speed extradition, a step he called usual practice. He said prosecutors would still investigate front men, corrupt officials or party figures who knowingly accepted illegal money.
Díaz heads the Public Prosecutor’s Office, part of the Judicial Branch, and is seeking a second term. The Supreme Court will vote on that term October 19.
The U.S. Case
Tam was arrested Friday, October 2, in Granadilla de Curridabat, an eastern suburb of San José. The U.S. federal court for Florida’s Middle District is seeking him under an indictment filed August 19. A confidential source said Tam offered to launder money, prompting the joint U.S.–Costa Rican investigation in October 2025.
An undercover agent later exchanged US$240,000 in Tether, a dollar-pegged cryptocurrency, for cash from Tam. Undercover buyers received about 6 kilograms of cocaine on January 15 and about 7 kilograms on February 16. Authorities seized both shipments. Agents told the courier the second load was bound for Florida. The case file says US$100,000 in cash went to a contact of Tam in Orlando on February 4. A second Costa Rican, Jeffry Oviedo Cerdas, is wanted in the same case.
Costa Rican prosecutors also link Tam to crime groups in Mexico and Colombia. CRHoy named the Sinaloa and Gulf cartels and Colombia’s Clan del Golfo, which Washington has listed as Foreign Terrorist Organizations since 2025.
A San José criminal court ordered two months of provisional detention Monday while the United States completes extradition papers. The Ministry of Justice and Peace, which runs the country’s prisons, ordered Tam placed under a maximum-security regime, citing his alleged links to groups tied to drug trafficking and money laundering.
Tam’s lawyer, Moisés Chinchilla, said the political questions are “a separate matter that has nothing to do with the process.” He added that U.S. authorities still have to file the documents supporting the charges.
Questions for the Governing Party
Tam appeared in photographs from the February 1 celebration at the Aurola hotel in San José, where Fernández marked her election victory. Fernández, of the ruling Pueblo Soberano party, succeeded Rodrigo Chaves and governs for the 2026–2030 term. One photo shows Tam with Pilar Cisneros, a former lawmaker who now advises the presidency on communications without pay. Cisneros told La Nación the photo is genuine, but she has never spoken to Tam.
Fernández first questioned whether the photo was real. “I do not know this person, I have not the slightest idea who he is,” she said Monday at the opening of a technical high school in Mora. She said about 2,000 people attended the party and she couldn’t know all of them.
Pueblo Soberano, led by party president and lawmaker Mayuli Ortega, rejected any suggestion of a financial relationship with Tam and offered to provide party records required by law. The party’s acting treasurer issued a certificate finding no donations, contracts, transfers or contributions under three versions of Tam’s name. Still, the party hasn’t explained why he attended the celebration, Teletica reported. Ortega said the campaign team, not the party, organised such events.
Finger-pointing has spread inside the party’s orbit. Cisneros said Ortega and party secretary general Freddy González should explain how Tam got into the event. Tam’s former partner, Kathleen Quirós, a Legislative Assembly employee, challenged González in a video: “I am not going to say, like Freddy, that I did not know him; I knew him,” she said, according to CRHoy.
What Remains Unknown
No extradition date has been set, and the full U.S. charging document hasn’t been published. The Prosecutor’s Office is awaiting the election-finance report and hasn’t said whom it will question. It’s also unclear who invited Tam. He hasn’t been convicted, and no government official or party member has been charged with a crime.
Díaz called Tam one of the “invisible narcos,” suspects without a visible criminal profile, and linked them to the second phase of his joint work with the DEA. Costa Rica extradited five men to the United States on October 1. The government plans to open a new high-security prison for organised crime on Wednesday, October 14.
Why This Matters:
The case tests whether Costa Rica’s institutions can police themselves when organised crime brushes against power. Prosecutors are investigating campaign financing, an area where the electoral tribunal’s records and the courts, not political statements, will settle the facts. No one in government has been charged, and the party’s treasurer found no financial ties. Those are the facts as they stand.
But a suspect in a U.S. cocaine and money-laundering case stood at the president’s celebration. Questions about the guest list remain unanswered, and they erode public trust. For a country courting investment and cooperating closely with U.S. law enforcement, the credibility of its rule of law is an economic asset. How transparently the inquiry proceeds, and whether it survives the politics around Díaz’s October 19 vote, will matter well beyond this one case.