Costa Rica’s chief prosecutor, Carlo Díaz, has opened an inquiry into Guobin Tam Zhang’s political ties after the U.S.-wanted drug suspect appeared in photographs at President Laura Fernández’s election victory party. Prosecutors are examining alleged money laundering and possible illegal campaign financing.
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 on October 2. No government official or party member has been charged, and Tam hasn’t been convicted.
The money trail
Díaz told La Nación he would investigate on his own initiative, without waiting for a complaint. “We are going to investigate any other background or relationship this person has at the political level,” he said. Before moving ahead with the campaign-financing inquiry, prosecutors are waiting for a report from the party-finance department of the Supreme Electoral Tribunal, Costa Rica’s election authority.
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 him. 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.
According to the case file, a contact of Tam received US$100,000 in cash in Orlando on February 4. A second Costa Rican, Jeffry Oviedo Cerdas, is wanted in the same case. The full U.S. charging document hasn’t been published, and officials haven’t set an extradition date.
Party records and unanswered questions
Photographs show Tam at the February 1 celebration at the Aurola hotel in San José, where Fernández marked her election victory. One photograph shows him alongside Pilar Cisneros, a former lawmaker who now advises the presidency on communications without pay. Cisneros told La Nación the photo is genuine, but said she’s 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. She said about 2,000 people attended the party and that she couldn’t know all of them.
Pueblo Soberano 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. Teletica reported that the party hasn’t explained why he attended the celebration.
Party president and lawmaker Mayuli Ortega said the campaign team, not the party, organised such events. Cisneros has 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, 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.
Extradition and the state response
On Monday, a San José criminal court ordered two months of provisional detention while the United States completes extradition papers, Teletica and CRHoy reported. 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 have to file documents supporting the charges.
The Ministry of Justice and Peace, which runs Costa Rica’s prisons, ordered officials to place Tam under a maximum-security regime, citing his alleged links to groups tied to drug trafficking and money laundering. Díaz said his office would suspend Tam’s local cases to speed extradition, describing this 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, part of the Judicial Branch, and is seeking a second term. The Supreme Court vote on that term is set for October 19. The Prosecutor’s Office hasn’t said whom it will question and is waiting for the election-finance report. Who invited Tam to the celebration is also unclear.
The U.S. federal court for Florida’s Middle District is seeking Tam under an indictment filed on August 19. Costa Rican prosecutors also link him 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.