The information was gathered during interviews with former detainees and prison guards. Only very few people managed to escape North Korea after having been released from one of the numerous political prison camps. The testimony of the former detainees draws a cruel picture. Prisoners are forced to work in conditions approaching slavery and receive only very little food and no clothing. All of the detainees have witnessed public executions in the camps.
The camps are believed to be running since the 1950s and some of them, labeled Total Control Zones, have been constructed for political prisoners with no perspectives of ever being released. The satellite images indicate that the scale of the prison camps has significantly increased since the last pictures in 2001.