Can crimes alleged to have been committed by senior leaders of the Khmer Rouge or others after 1979 be tried?

No, this court can try only crimes committed in Cambodia between 17 April 1975 and 6 January 1979.  Prior to the establishment of the ECCC, the existing Cambodian courts tried some crimes alleged to have been committed by the Khmer Rouge after 1979. For example, the trial of Khmer Rouge officers responsible for ambushing the Phnom Penh-Kampot train in 1994, killing 11 Cambodians and executing three Western hostages, took place in the normal Cambodian courts.