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 at President Laura Fernández’s election victory party. Tam was arrested near San José three days before Díaz announced the investigation on Monday, October 5. Prosecutors will examine possible illegal financing of the last election campaign and money laundering.
One question hangs over the celebration: who brought Tam into a room full of political power? No one has answered. Tam’s former partner, Kathleen Quirós, a Legislative Assembly employee, challenged party secretary general Freddy 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.
A campaign under scrutiny
Díaz told La Nación he would open the investigation 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. Prosecutors first need a report from the party-finance department of the Supreme Electoral Tribunal, Costa Rica’s election authority. The Prosecutor’s Office hasn’t said whom it will question, and it’s unclear who invited Tam.
With a judge’s approval, investigators opened five devices seized from Tam, including four phones. Díaz said the findings could lead to cases against other people. His office will suspend Tam’s local cases to speed extradition, he said, describing that as usual practice, while continuing to investigate front men, corrupt officials or party figures who knowingly accepted illegal money.
Pueblo Soberano, led by party president and lawmaker Mayuli Ortega, rejected any suggestion of a 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 any of 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. Pilar Cisneros, a former lawmaker who now advises the presidency on communications without pay, said the photograph of her with Tam was genuine, but she had never spoken to him.
The machinery around the case
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. On Monday, a San José criminal court ordered two months of provisional detention while the United States completes extradition papers. No extradition date has been set, and the full U.S. charging document hasn’t been published. Tam hasn’t been convicted, and no government official or party member has been charged with a crime.
A confidential source told investigators in October 2025 that Tam offered to launder money, prompting the U.S. and Costa Rican investigation. An undercover agent later exchanged US$240,000 in Tether for cash from him. Undercover buyers received about 6 kilograms of cocaine on January 15 and about 7 kilograms on February 16; agents seized both shipments. Agents told the courier the second load was bound for Florida. According to the case file, someone delivered US$100,000 in cash to a contact of Tam in Orlando on February 4. A second Costa Rican, Jeffry Oviedo Cerdas, is wanted in the same case.
Costa Rica’s Ministry of Justice and Peace, which runs the country’s prisons, ordered Tam placed under a maximum-security regime on Monday, citing his alleged links to groups tied to drug trafficking and money laundering. 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.
Elections, official denials and unanswered questions
Photographs show Tam at 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. At the opening of a technical high school in Mora, she 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 and she couldn’t know all of them.
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. Díaz heads the Public Prosecutor’s Office, part of the Judicial Branch, and is seeking a second term; a Supreme Court vote on that term is set for October 19. Costa Rica extradited five men to the United States on October 1. Prosecutors’ inquiry into Tam’s political connections now hinges on a finance report, findings from seized devices and questions they haven’t yet said they’ll ask. The party offered records. The invitation remains unexplained.