Youlin Chen, an American scientist born in China, has been detained by Chinese authorities since late 2024 and charged with espionage. This week, after nearly two years of silence, his family publicly called for his release—revealing a case the Chinese government had kept secret.

Chen, who lives in Boston, is a seismologist: someone who studies earthquakes and underground vibrations. His research focused on detecting and analyzing North Korean nuclear weapons tests. He published his findings using data from monitoring stations funded by the US government. Here's how it works: when a nuclear bomb explodes underground, it sends out waves of energy—similar to an earthquake—that scientists can measure and detect. These waves have distinctive patterns that allow researchers to tell them apart from natural earthquakes. Chen used international monitoring networks to study the force and structure of North Korea's nuclear tests.

This work sits at a tricky boundary. Chen's research was published openly in scientific journals, but the US government also funded some of it because understanding nuclear weapons has military importance. China appears to view this kind of work as espionage, even though the findings were publicly available. According to China's espionage laws, scientific research can be treated as illegal if it relates to national security—and a neighboring country's nuclear program certainly qualifies.

When foreign nationals are detained in China on security charges, the detentions can remain secret for months or years. Families are often told by lawyers or their own governments to say nothing publicly, hoping that quiet talks behind the scenes will work better. Chen was held this way for nearly two years. His family decided to speak out now because a trial date was approaching and they saw no sign the Chinese government planned to release him.

China has detained foreign researchers, business people, and dual citizens on national security grounds before, especially during tense periods in US-China relations. The US has sometimes called these wrongful detentions and worked to free the people through prisoner exchanges. Whether that will happen in Chen's case depends partly on how bad US-China relations are at any given moment—not just on the charges against him.

By going public, Chen's family has shifted the case from a private diplomatic matter into public view. This kind of announcement sometimes leads either to faster trials or to secret negotiations for release. For now, no one knows which path this case will take.