The four defence lawyers for Kem Sokha on Thursday walked out of the courtroom to express frustration with the trial chamber that they said had refused to let them respond to the prosecutor and government lawyers.

The trial on Thursday saw a series of tense debates over the use of a one-page document by the prosecutors as evidence. The defence team alleged irregularities, saying they had never seen the document before and asked the judges to ensure transparency by disclosing it.

The walkout came just an hour before the hearing closed and prompted the judges to call them “gang lawyers”.

“Note their aggressive behaviour in the court file. The lawyers must be disciplined on morality,” trial chamber president Koy Sao said.

The trial continued despite the defence team’s protest.

Presented by prosecutor Plang Sophal as evidence, the one-page document centred on a joint statement made by the Sam Rainsy Party (SRP) and Human Rights Party (HRP) over the establishment of the Cambodia National Rescue Party (CNRP).

Sokha’s defence team told Judge Sao that they were not provided with the document that the prosecutor was using as evidence. They requested the trial chamber to make it available to them too.

Even after the trial chamber, prosecutor and government lawyer raised the document to indicate that they all had it, the defence team insisted they could not find it in the evidence files provided by the court.

The defence team said they were suspicious that the document had been filed only recently because they found a different registration number on it after verification. They requested the trial chamber show “integrity” in using the document as evidence.

Both the trial chamber and the prosecution argued that the document was in the original court files and that they had no reason to secretly add more documents as claimed.

Judge Sao confirmed that the document was available in both hard and soft copy contained on a disc stored since before the start of the treason trial. He said the defence team either failed to request a copy from the court of simply lost it.

The prosecution and government lawyer alleged that the defence team had frequently cited a lack of documentation since the first day of trial, causing a repeated delay of questioning for Sokha.

When Sokha’s lawyer repeatedly requested the court to respond to their allegation of irregularities, Judge Sao ordered them to stop talking, prompting them to walk out in protest.

When asked by Judge Sao if the allegation was true, the court clerk acknowledged he had not copied all documents for the lawyers, possibly leaving them without one.

Judge Sao then ordered the clerk to retrieve a copy of the document in the original court file and play the disk to prove the court’s integrity in the absence of Sokha’s lawyers.

After the disk was played, Judge Sao let Sokha decide if he still wanted the four lawyers as his defence team or find a new one. He said the hearing will not resume next week to give Sokha more time to find new lawyers, should he desire, and request copies of documents that he had not received from the court.

Sokha said he will consult with the four lawyers to make sure the next hearing proceeds smoothly, at which point Judge Sao warned of legal action should the defence boycott the next trial.