They will determine which complainants can participate in Case 002 when it goes to trial as early as next year.
JCE considers members of an organized groups and makes them individually responsible for crimes committed or planned by the group.
Besides bringing senior leaders to trial, the tribunal was also meant to bring a measure of reconciliation to the country.
Defense also cited reported errors by the Trial Chamber in determining his original non-commuted sentence of 35 years.
Joint Criminal Enterprise is a complex legal theory that groups suspects together in the planning and execution of crimes.
The tribunal has so far tried one suspect, Duch, and it is preparing for the potential joint trial of four more senior leaders.
Nearly 40,000 Cambodians live Lowell, and many of them were also victims of the Khmer Rouge.
A recent screening, in Battambang province's Samlot district, took place at a church five minutes from Duch's former home.
The administrative announcement comes a day after all four were indicted by prosecutors, who sent in their final submissions on Monday.
Duch was given a commuted sentence of 19 years for his role in the torture and execution of more than 12,000 people.
An estimated 2 million people, or a quarter of the population, perished under the regime.