The working group interviewed 375 defectors from North Korea over the past two years. They were shown maps of their home towns and asked to identify places where abuses occurred. The researchers say they have been able to pinpoint 47 sites where bodies were buried or dumped, and hundreds more that might yield documentary evidence in the future.

There is no sign that Kim Jong Un, the third-generation leader of North Korea, or his regime is going to change or collapse anytime soon, but Son said it is not too early to plan.

“People who have done this kind of work in Croatia or Southeast Asia keep telling us we can’t be too prepared for what might happen in the future,” she said.