Together, the two sisters and their husbands later became known as "Cambodia's Gang of Four", a reference to the radical group led by Jiang Qing (Chiang Ching), the widow/wife of Chinese communist leader Mao Tse-tung.

By 2006, Ieng Thirith and her husband had retained foreign legal counsel to assist with their defence as the Cambodia Tribunal made progress with courtroom preparation and judge selection.

[13] She was arrested for crimes against humanity:[14] "planning, direction, coordination and ordering of widespread purges ... and the unlawful killing or murder of staff members from within the Ministry of Social Affairs.

"[7] On 17 November 2011, Thirith was ruled mentally unfit to stand trial, due to her severe case of Alzheimer's disease, and was ordered to be released.

[15] On 13 December 2011, appeals judges reversed the ruling to release Thirith and ordered new medical exams to see how mentally fit she was to stand trial.