Khieu Samphan’s lawyers have asked that 14 US cables made accessible in April by whistleblower website WikiLeaks be considered by the Khmer Rouge tribunal, according to a recent prosecutors’ filing objecting to two of these cables that “relate to alleged political interference and corruption at the ECCC”.

The first of these cables, sent to Washington from then US ambassador Joseph Mussomeli in 2006, states that new staff in the Cambodian prosecutor’s office “are considered politically biased and easily influenced by the government”.

The second, from Mussomeli in 2007, raises questions about Cambodia’s commitment to the tribunal after a series of “Cambodian mis-steps and mis-statements”, such as the appointment of co-investigating judge You Bunleng to presidency of the domestic Appeal Court, which threatened to conflict with his position at the tribunal.

The prosecutors say these cables are “irrelevant, repetitious, unsuitable to prove the facts they intend to prove, and/or frivolous”.

“This Chamber has previously held that outside opinions ‘regarding the fairness of proceedings at the ECCC... have no evidential value’,” they add.

Samphan’s lawyers argue that the 12 other cables they seek to admit, dated 1973-1976, show their client’s good character and limited power, the filing says.

The prosecutors note that the defence has opposed as biased or unsuitable all 26 cables the prosecution has asked to admit, including some referring to Khmer Rouge executions of civilians.