Chinese-American seismologist Youlin Chen has been detained in China since November 2024 on espionage charges
Chen is known for publicly available research on detecting North Korean nuclear tests commissioned by the US State Department
The US has designated him as "wrongfully detained" and raised his case with Beijing
In November 2024, Youlin Chen arrived at Beijing Capital Airport with a ticket to Boston. He had spent time in China visiting family and delivering lectures on his seismological research at two universities. Before boarding, state security officers stopped him at the gate and he has remained in China ever since.
Chen, 54, is a Chinese-born American seismologist whose published research on detecting North Korean nuclear tests had attracted attention well beyond the academic community. By May 2025, he had been formally charged with espionage however, he has not yet stood trial.
The detention has cost him more than freedom. His wife, Yufang Rong, herself a seismologist told Reuters that in the early weeks he was forced to sit on a hard stool throughout the day, prohibited from standing, reading or exercising. His diabetes medications were withheld. Since then, she said, he has lost between 13.6 and 18.1 kg. The food he receives is insufficient. The medications are poor quality.
"I believe they will convict him no matter what," Rong added, "and the trial will be behind closed doors."
The Work
Chen built his career at the intersection of seismology and arms control, studying how to identify underground nuclear detonations and separate their signals from those of natural earthquakes.
His most cited work in this context is a December 2020 paper that examined the magnitude of North Korea's six known nuclear test blasts. The paper mapped methods for distinguishing their seismic signatures from earthquakes. On its cover page, it states it was written for the State Department's arms control bureau. It was, the same page notes, "approved for public release."
That detail sits at the heart of the case. Chinese interrogators have questioned Chen more than 100 times, specifically about his work on North Korean nuclear test seismic signatures, said Rong. The research was commissioned by and cleared for publication by an arm of the US government. It was publicly available. Beijing, however, appears to view it through a different lens.
The Legal Mechanism
China's state secrets law gives authorities broad powers to retroactively classify previously open information, including official statistics or published studies as national security secrets, human rights groups have argued. Under that logic, anyone who gathered or shared data that is later reclassified can potentially face criminal exposure, regardless of what the material's public status was at the time.
Chen's research connects seismology directly to nuclear monitoring; an area with clear intelligence and military implications. That overlap, rather than the publication status of his work, appears to be what drove the espionage allegation.
A Case Within A Relationship
US Secretary of State Marco Rubio designated Chen as "wrongfully detained" in March 2026, making his release a formal US government priority. A US source familiar with the matter told Reuters that the administration was "focused on gaining his release from his unjustifiable detention."
The Trump administration, however, made a deliberate choice to keep the designation quiet. Space was needed for high-level diplomacy to work, according to Rong’s comment.
That diplomacy reached its most visible moment in May 2026, when President Trump visited Beijing, the first visit by a sitting US President to China since 2017. Trump raised Chen's case directly with President Xi Jinping which he promised to look into but nothing followed.
The same summit produced a package of economic agreements. According to official White House documents, China committed to purchase at least $17 billion per year in US agricultural products through 2028, placed an initial order for 200 American-made Boeing aircraft and restored access for US beef and poultry.
The Numbers Behind The Relationship
The weight of that relationship is measurable. US goods and services trade with China totalled an estimated $658.9 billion in 2024, according to data by the US Trade Representative (USTR). In 2025, US goods trade with China reached $414.7 billion, with the goods deficit narrowing to $202.1 billion, a 31.6% decrease from 2024.
That commercial relationship has its own turbulent history. Section 301 investigations under Trump's first term triggered tariffs that escalated into a sustained trade war from 2018. The Phase One deal signed in January 2020 set out purchase commitments from Beijing that went largely unmet. The current May 2026 agreements are an attempt to rebuild on that fractured foundation, even as individual cases like Chen's expose the limits of the partnership.
The Wider Friction
Chen is not alone. The Foley Foundation, a hostage advocacy organisation, believes he is among at least 12 Americans unjustly held in China, including those under exit bans. "President Trump has been clear that he wants every American detained abroad to return home, and he has reunited over 100 individuals with their families since taking office this term," deputy White House press secretary Anna Kelly said.
The broader US-China relationship carries its own load. On Monday, 14 countries — including the US, Japan and Australia, jointly reaffirmed the 2016 South China Sea arbitration ruling and rejected Beijing's expansive maritime claims. China dismissed the ruling as a "worthless piece of paper." Just a few days earlier, China had test-fired a submarine-launched ballistic missile into the southern Pacific, a launch the US characterised as an intercontinental ballistic missile.
China's Foreign Ministry denied any wrongdoing in Chen's case specifically. "China's judicial organs handle cases according to the law and there is no so-called wrongful detention," spokesperson Lin Jian said at a regular briefing.
What Awaits
Chen's trial has no confirmed date. If convicted on espionage charges, he faces up to life in prison. In cases Beijing deems especially grave, the death penalty applies.
His case is expected to arise again when Xi visits Washington in the autumn. Whether that conversation moves differently from the one in Beijing in May remains the central unknown.
Rong has watched 100 interrogations. She has watched her husband lose weight across two years of detention. She has watched a summit come and go. "I believe they will convict him no matter what," she told Reuters.
