Yribe responded with Spielman, 22, of Chambersburg, Pa., and two others after Iraqi soldiers reported the slayings in Mahmoudiya.
He testified that Green and Sgt. Paul E. Cortez were waiting for him at a checkpoint after Yribe went to the scene, and that Green immediately told him he had attacked the family.
"I didn't believe him at all," Yribe said. He said he thought such an attack was improbable in broad daylight in a particularly violent region.
Prosecutors displayed grisly photographs of 14-year-old Abeer Qassim al-Janabi, her parents and younger sister as Yribe described the scene. The photo of Abeer showed a charred outline of the girl's upper body. Her legs and the remnants of a blue and purple dress were all that weren't burned.
Spielman faces rape and murder charges, and he pleaded guilty to lesser charges on Monday. Prosecutors do not say he took part in the rape or murders, but he can be charged under military law if they can prove he went to the house knowing what the others intended to do.
Other soldiers charged in the attack have told investigators that Spielman knew of the plan to rape the girl, and that he was present when they hammered out details over swigs on a bottle of Iraqi whiskey.
During their courts-martial, Spc. James P. Barker and Cortez testified they took turns raping the girl while Green shot and killed her mother, father and younger sister. Green shot Abeer in the head after raping her, they said. The girl's body was then set on fire with kerosene to destroy the evidence, according to previous testimony.
Barker, Cortez and Pfc. Bryan L. Howard are expected to be called to testify against Spielman.
The three soldiers have pleaded guilty for their roles in the slayings and received sentences of five to 100 years. Green, who was discharged from the Army before being charged, faces the possibility of the death penalty when he is tried in federal court.
Green has pleaded not guilty to charges that include murder and sexual assault. No trial date has been set, and his attorney Patrick Bouldin declined to comment Tuesday.
Maj. Alex Pickands, an Army prosecutor, said in his opening statement that the unit's discipline had begun to unravel in the violent rural area south of Baghdad.
Defense lawyer Dan Christensen said the unit was filled with soldiers who struggled with mental disorders and took drugs and alochol to cope with a battlefield that had killed dozens of their friends.
"Every person involved in these allegations had been diagnosed with a mental disorder by March 12," he said.
Spielman pleaded guilty Monday to conspiracy to obstructing justice, arson, wrongfully touching a corpse and drinking.
Christensen told jurors Spielman "made some really bad judgment calls, and you're going to see that he's admitted to them."
