On 28 November 2019, a hearing will begin before the Pre-Trial Chamber (PTC) of the Extraordinary Chambers in the Court of Cambodia (ECCC) in Case 003, the MEAS Muth case (see here while for an overview of the proceedings in the ECCC, see here). The hearing is an appeal of the two separate closing orders of the national and international co-investigating judges of November 28, 2018 resulting from a disagreement between them about whether MEAS Muth was subject to the ECCC’s personal jurisdiction as “a senior leader or one of the persons most responsible for crimes committed during the period of 17 April 1975 to 6 January 1979 in the Democratic Kampuchea” (DK)(article 2 of the law establishing the ECCC, see here). As this issue is also at the heart of the two other remaining cases before the ECCC, namely the YIM Tith and AO An case and the PTC has already found that another person, IM Chaem, did not fall within this category (see here), an overview of this notion of ‘most responsible’ is timely.