Costa Rica’s attorney general will investigate whether a naturalized Costa Rican detained for extradition to the United States had political ties or helped finance last February’s presidential campaign, after he was photographed at President Laura Fernández’s election-night celebration.
Guobin Tam Zhang, 54, who also uses the name Juan Carlos Tam Cheong, was detained Oct. 2 in Granadilla de Curridabat at the request of the U.S. government. He is sought by the United States in connection with alleged international drug trafficking, and Costa Rican prosecutors say he also faces a local investigation for alleged money laundering.
The Ministry of Public Security described Tam as one of the main launderers of drug-trafficking proceeds here. According to the ministry, he allegedly coordinated cocaine shipments bound for the United States and then handled payments for those shipments on behalf of the cartels involved.
The arrest was carried out jointly by the Public Prosecutor’s Office, the Drug Control Police, the Fuerza Pública, the U.S. Drug Enforcement Administration (DEA) and the U.S. Treasury Department.
On Monday, the San José Criminal Court ordered two months of provisional detention while the extradition request proceeds, according to Tam’s lawyer, Moisés Chinchilla. Chinchilla said the court informed his client of the DEA file during the hearing, and that the United States must still submit formal documentation and the evidence supporting its request.
The same day, the Ministry of Justice and Peace ordered Tam into the prison system’s high-containment circuit. The ministry said he met the criteria because of his alleged links to criminal structures, and that he will be held in an individual cell with controls on his visits, calls, contacts and personal belongings.
Attorney General Carlo DÃaz said Monday that prosecutors will open an investigation on their own initiative into any political relationships Tam may have had, with a focus on money laundering and possible illegal campaign financing. DÃaz said prosecutors will first await a report from the Supreme Elections Tribunal’s department that oversees political party financing.
DÃaz said Costa Rica will prioritize sending Tam to the United States, applying a prosecutorial discretion rule that suspends local cases against an extraditable defendant. He said, however, that anyone found to have assisted Tam, including front men, corrupt officials or party representatives who knowingly accepted illegal money, would face investigation.
The attorney general also said a judge has authorized prosecutors to open five electronic devices seized from Tam, four of them cellphones, and that any evidence of crimes by other people would lead to new cases. DÃaz linked the arrest to the second phase of a joint strategy with the DEA aimed at what he calls invisible narcos, people who would not be identified as possible traffickers without an investigation.
The case turned political after a photograph circulated showing Tam beside Pilar Cisneros, a former lawmaker who now advises the presidency on communications, at the Feb. 1 event at the Aurola hotel in San José where Fernández received the election results. Local reports say Tam was inside rooms reserved for campaign staff, party leaders and invited guests. The mother of two of Tam’s children also attended and was photographed with Fernández, according to those reports.
Fernández said Monday that she does not know Tam, has never met with him and does not know what he does for a living. Cisneros said she does not know him either and that many people approached her for photographs that night.
The two have given differing accounts of the photograph itself. Speaking yesterday in Mora, Fernández said she did not know whether the image circulating of Tam with Cisneros was authentic, adding that about 2,000 people attended the celebration and she did not know all of them. Cisneros, however, has confirmed that the photograph is genuine and was taken that night at the Aurola, while maintaining that she has never spoken with Tam.
The ruling Pueblo Soberano party issued a certification from its treasurer, Raúl Zamora, stating that party records show no donations, contracts, transfers or other transactions involving Tam under any of the names he uses. Party president Mayuli Ortega said neither she nor the party has any relationship with him, and secretary general Freddy González said Tam was not on the party’s guest list for the celebration.
Opposition lawmakers have demanded further explanations. Liberación Nacional legislator Marco Badilla said the Legislative Assembly’s Security and Drug Trafficking Commission will examine the case, and fellow party legislator VÃctor Hidalgo formally asked the presidency whether Tam was invited to the May 8 transfer of power or has visited executive branch offices.
Frente Amplio leader José MarÃa Villalta called on the government and the party to explain Tam’s presence at official events, while Claudia Dobles, head of the Coalición Agenda Ciudadana caucus, asked the Supreme Elections Tribunal to examine campaign financing. Pueblo Soberano caucus leader Nogui Acosta questioned whether the Legislative Assembly should investigate, saying the faction has no relationship with Tam.
In a sworn statement dated Aug. 4, 2025, Tam declared that all his income came from lawful activities, mainly the rental of commercial premises and homes on properties he represents or manages. Public records reviewed by local media show no properties registered in his name or in companies where he sits on the board.
Tam has not been convicted of any crime. His case is one of a series of U.S. extradition requests Costa Rica has handled this year in connection with drug investigations, including the 24 requests under review as of August and the prosecution of former magistrate Celso Gamboa in Texas.
