The commission of genocide and other large-scale international crimes typically involves a multitude of perpetrators acting in concert. As such, the pursuit of individual criminal accountability following the perpetration of mass crimes has involved oft-controversial decisions of whom to prosecute. This challenge is exemplified by the ongoing controversy in Cambodia concerning the proper scope of prosecutions at the Extraordinary Chambers in the Courts of Cambodia (ECCC) for the crimes of the Khmer Rouge regime from 1975-1979, as the Court’s third and fourth cases have languished amidst considerable controversy for years. This paper examines whether the presumed suspects in the two cases legally qualify as individuals “most responsible” for the crimes of the Khmer Rouge period in Cambodia by considering known information about each suspect in light of available international criminal law jurisprudence and argues that all suspects fall well within any reasonable legal definition of the term “most responsible” as each is implicated directly in extremely grave crimes. As such, it is concluded that there is no viable legal alternative available to bring the two cases to a close save for trial.