Torture, hunger and hard labour is allegedly part of life for detainees in North Korean political prison camps.
Over the next few days, defectors are giving their personal account to a panel of United Nations investigators looking at human rights abuses in North Korea.
The Commission of Inquiry has little power, but some are hoping it can put pressure on North Korea.
Al Jazeera's Florence Looi reports from Seoul.
Source: Al Jazeera