In the small number of trials for matters such as genocide and crimes against humanity that have taken place before the Extraordinary Chambers in the Courts of Cambodia, by 2014 three occasions had arisen in which the fitness of the accused persons to participate in their trials had become contentious. This is hardly surprising given that the key period of Khmer Rouge government occurred a very long while ago--between 1975 and 1979. The accused persons are all aged. In two instances, the Trial Chamber of the Courts of its own motion sought expert evaluations of the accused persons' fitness to stand trial and, promptly, upon receipt of such reports, determined them to be fit by reference to criteria utilised by the Appeal Chamber of the International Criminal Court for the Former Yugoslavia (the ICTY). In the other instance an accused person, leng Thirith, was found unfit to stand trial and a range of important issues was traversed as to the measures that can properly be taken to try to render a person fit for trial and how legitimate the imposition of detention for that purpose is, and then how legitimate encroachments on a person's civil liberties are to monitor them if there is only a remote possibility that their mental state might improve. It is likely that the balance adopted by the Supreme Court Chamber in the Courts of Cambodia in making significant efforts to render an accused person fit for trial and then in continuing to monitor their mental state when such efforts do not bear fruit, instead of simply releasing them back into the community, will stand as an important precedent for future occasions under international criminal law when issues of fitness to stand trial and how they should be handled arise.