Youlin Chen, 54, a U.S. citizen who lives in Boston, Massachusetts, was arrested by Chinese state security officers on Nov. 5, 2024, at Beijing International Airport as he prepared to return to the United States after visiting family and delivering lectures at two Chinese universities, according to his wife, Yufang Rong, and hostage advocate Eric Lebson.

U.S. Secretary of State Marco Rubio designated Chen as “wrongfully detained” on March 19, elevating his release as a priority for the U.S. government. Rong said the Trump administration has not publicly announced the designation in order to preserve space for diplomatic efforts aimed at securing her husband’s release.

A U.S. official familiar with the matter said the administration remained focused on obtaining Chen’s release from what it described as an unjustified detention but declined to discuss sensitive diplomatic exchanges.

According to Rong, President Donald Trump raised Chen’s detention during a state visit to Beijing in May, where Chinese President Xi Jinping said he would look into the case. Reuters could not independently confirm that account, although the U.S. source said Chen’s detention was among numerous issues in the broader U.S.-China relationship and that no single issue defined bilateral ties.

Chen is currently the only American in China formally designated by Washington as wrongfully detained, according to his wife and hostage advocacy groups. The Foley Foundation, which tracks Americans held abroad, believes at least 12 U.S. citizens are being unjustly held in China, including individuals subject to exit bans.

Rong said she fears Chinese authorities have already decided the outcome of her husband’s case before trial. She believes proceedings will be conducted behind closed doors, noting that espionage convictions in China can carry sentences ranging from lengthy imprisonment to life in prison or, in especially serious cases, the death penalty.

According to Rong, Chinese investigators have questioned Chen more than 100 times about his research into the seismic signatures of North Korean nuclear tests.

Eric Lebson, whose organization Global Reach is assisting Chen’s family, said he believes Chinese authorities are interested in Chen’s scientific expertise regarding techniques used to detect underground nuclear tests. Lebson said Chen’s work relied on publicly available data, was conducted in collaboration with Chinese academics, and never involved classified information.

Chen is employed by a U.S. government contractor but has never held a U.S. security clearance or performed classified work, Lebson said. His research received funding from the U.S. State Department and the Air Force Research Laboratory.

A 2020 paper reviewed by Reuters analyzed seismic data from North Korea’s six known nuclear tests and methods for distinguishing nuclear explosions from earthquakes. The document stated that it had been prepared for the U.S. State Department’s Bureau of Arms Control and was approved for public release.

Human rights organizations have argued that China’s state-secrets legislation gives authorities broad powers to retroactively classify previously public information as national security secrets, potentially exposing researchers who relied on open-source material to criminal prosecution.

Rong said her husband initially endured harsh detention conditions, including prolonged periods of forced sitting without access to reading materials or exercise. She said he was also denied medication for diabetes and other health conditions during the early months of his detention.

She added that Chen has since lost between 30 and 40 pounds while in custody and receives inadequate food and poor-quality medication. U.S. embassy officials have visited him several times, she said, but Chinese officials have always been present, preventing private conversations. His Chinese lawyer was permitted to meet him only after more than 13 months in detention.

Chen was formally charged with espionage on May 1, 2025, but has not yet been brought to trial. U.S. Senator Ed Markey, who led a bipartisan appeal urging the State Department to designate Chen as wrongfully detained, said he remained deeply concerned about the scientist’s safety and wellbeing and expressed hope that increased international attention would lead to his release.