Costa Rica’s chief prosecutor, Carlo Díaz, opened an inquiry into Guobin Tam Zhang’s political ties after the U.S.-wanted drug suspect appeared in a photograph from President Laura Fernández’s election victory party. The investigation will examine possible money laundering and illegal financing of the last election campaign as U.S. authorities seek Tam’s extradition under a Florida federal indictment.
The Costa Rican inquiry
On Monday, October 5, Díaz said he would launch the investigation on his own initiative instead of waiting for a complaint. “We are going to investigate any other background or relationship this person has at the political level,” he told La Nación.
The Prosecutor’s Office is awaiting a report from the party-finance department of the Supreme Electoral Tribunal, Costa Rica’s election authority. With a judge’s approval, Díaz said, investigators opened five devices seized from Tam, four of them phones. Their findings could lead to cases against other people.
Díaz said his office would suspend Tam’s local cases to speed up extradition, a step he described as usual practice. Prosecutors would still investigate front men, corrupt officials or party figures who knowingly accepted illegal money, he said. Díaz heads the Public Prosecutor’s Office, which forms part of the Judicial Branch, and is seeking a second term. The Supreme Court is set to vote on that term on October 19.
The U.S. case and extradition
Tam, also known as Juan Carlos Tam Cheong, was born in China and became a naturalised Costa Rican. Authorities arrested him in Granadilla de Curridabat, an eastern suburb of San José, on Friday, October 2. The U.S. federal court for Florida’s Middle District seeks his extradition under an indictment filed on August 19, which alleges drug trafficking and money laundering. Tam hasn’t been convicted, and authorities haven’t published the full charging document.
The U.S. and Costa Rican investigation began in October 2025 after a confidential source said Tam offered to launder money. 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 that the second load was bound for Florida. According to the case file, US$100,000 in cash reached 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, along with Colombia’s Clan del Golfo, which Washington has listed as Foreign Terrorist Organizations since 2025. On Monday, a San José criminal court ordered two months of provisional detention while the United States completes extradition papers. Tam’s lawyer, Moisés Chinchilla, called the political questions “a separate matter that has nothing to do with the process.” He said U.S. authorities still had to file documents supporting the charges.
The party photographs and party response
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 photograph shows Tam alongside Pilar Cisneros, a former lawmaker who advises the presidency on communications without pay. Cisneros confirmed the photograph but said she’d never spoken to Tam.
Fernández initially questioned whether the photograph was real. “I do not know this person, I have not the slightest idea who he is,” she said, according to La Nación. About 2,000 people attended, she said, and she couldn’t know all of them.
Led by party president and lawmaker Mayuli Ortega, Pueblo Soberano denied any financial relationship with Tam and offered to provide records required by law. A certificate from the party’s acting treasurer found no donations, contracts, transfers or contributions under three versions of Tam’s name. The party hasn’t explained why he attended the celebration. Ortega said the campaign team, not the party, organised such events. Cisneros said Ortega and party secretary general Freddy González should explain how Tam entered the event. Tam’s former partner, Kathleen Quirós, a Legislative Assembly employee, said in a video: “I am not going to say, like Freddy, that I did not know him; I knew him,” according to CRHoy.
No extradition date has been set, and prosecutors haven’t said whom they’ll question. No government official or party member has been charged. On Monday, the Ministry of Justice and Peace ordered Tam placed under a maximum-security regime, citing his alleged links to groups tied to drug trafficking and money laundering.