The agents, Ronald C. Eowan and Paul Ryan Mayers, helped arrest the seven suspects, including alleged ringleader Antonius Wamang, in Timika, Papua, in January.
They lured the suspects from their hiding place by promising asylum in the U.S., where they would not be prosecuted. After the Papuans came out with their bags packed, the agents turned them over to the police.
"This man is a liar!" defendant Ishaq Onawame cried when Eoman entered the courtroom. "I want him out or we will get out of here!"
But Judge Andriani Nurdin ignored the defendants' protests and allowed the agents to testify. Infuriated by the judge's decision, the defendants stormed out of the courtroom. Their lawyers from the Indonesian Legal Aid Association followed.
Defense lawyer Johnson Panjaitan said the court had violated Article 60 of the Criminal Code, which stipulates that prosecutors should summon eyewitnesses. "I don't see the point in bringing them to testify in the trial," he told The Jakarta Post. "What kind of witnesses are they?"
Anita Asterida, one of the prosecutors, said there were many ways to prove a criminal act, including presenting the FBI agents who made the arrest possible. "We have to show that Indonesia is a member of Interpol, which facilitates investigations," she told the Post, adding that the prosecutors would present another FBI agent to testify in the trial on Friday.
All but one of the defendants have denied involvement in the deadly shooting near the site of mining giant PT Freeport Indonesia. In a video played during the session, Wamang told FBI agents and police that he had fired shots during the ambush at Tembagapura, killing U.S. nationals Ricky Lynn Spier, 44, and Edwin Leon Burgen, 71, and Indonesian FX Bambang Riwanto.
Survivors of the attack, including Patsy Spier, Kenneth Ball and Stephen Emma, who testified earlier in the trial, attended Tuesday's session. "I'll be here for the whole trial. I want to make sure that the trial is fair and transparent," Spier told the Post. One of the seven defendants was absent Tuesday.