The Santebal was in charge of internal security and running prison camps like Tuol Sleng (S-21) where thousands of people were imprisoned, tortured and killed. It was part of the Khmer Rouge organizational structure well before April 17, 1975 when the Khmer Rouge took control over Cambodia. The name is an amalgam of two words: santisuk meaning security and norkorbal meaning police.
As early as 1971, the Khmer Rouge established the Special Zone outside of Phnom Penh under the direction of Vorn Vet and Son Sen. Son Sen, later the Deputy Prime Minister for Defense of Democratic Kampuchea, was also in charge of the Santebal, and in that capacity he appointed Comrade Duch to run its security apparatus. When the Khmer Rouge took power in 1975, Duch moved his headquarters to Phnom Penh and reported directly to Son Sen. At that time, a small chapel in the capital was used to incarcerate the regime's prisoners, who totaled fewer than two hundred. In May 1976, Duch moved his headquarters to its final location, a former high school known as Tuol Sleng, which could hold up to 1,500 prisoners. It was at Tuol Sleng that the major purges of Khmer Rouge cadres took place and thousands of prisoners were tortured and killed. Between 1976 and 1978, 20,000 Cambodians were imprisoned at Tuol Sleng. Of this number only seven adults are known to have survived.
- Nic Dunlop (2005)). The Lost Executioner - A Journey into the Heart of the Killing Fields. Walker & Company, New York. ISBN 0-8027-1472-2.
- Bizot, François; translated from French by Euan Cameron (2003). The Gate. Alfred A. Knoph. ISBN 0-375-41293-X.