Duch is scheduled to testify at the court on Monday in the atrocity crimes trial of Nuon Chea, Khieu Samphan and Ieng Sary.
Cambodian prosecutors presented a list of experts to the Trial Chamber of the court who could affirm the authenticity of the documents.
Defense lawyers for Nuon Chea and Ieng Sary also objected to prosecution documents on Tuesday.
The classes are attended mainly by foreign tourists and held in the group’s former torture center.
Kaing Kek Iev, better known as Duch, is set to testify on March 20 in the case against leaders Nuon Chea, Khieu Samphan and Ieng Sary.
In a phone interview, Ellis told VOA Khmer the court’s credibility is failing and that more international support is needed.
An investigation team read the notification order to Im Chaem at her home in Uddor Meanchey province on February 28.
Cases 003 and 004 involve five mid-level Khmer Rouge leaders who are currently living freely in the country.
The tribunal has received heavy criticism over political interference related to cases 003 and 004.
Donors are meeting in New York on Friday to review the budget proposal.
The court’s international side is expected to run out of funds in a few months, if more funding is not allocated.
In his confession during a hearing in March 2009, Duch said he reported to brother number two Nuon Chea, the regime’s chief ideologue.