The trial of General Efrain Rios Montt, 86, the former US-backed de facto president of Guatemala, has begun over the killing of almost 1,800 indigenous people during his country's civil war.
Rios Montt, 86, seized power in a coup in March 1982 and ruled until he was overthrown in August 1983.
Prosecutors alleged on Tuesday that Rios Montt "turned a blind eye" as soldiers used rape, torture and arson against leftist fighters and targeted indigenous people in a "scorched earth" offensive that killed at least 1,771 members of the Mayan Ixil group.
Nicolas Brito, an indigenous Ixil, was the first of at least 150 witnesses expected to give their testimony in the trial of the first Latin American leader to be tried on genocide charges in his own country.
Brito told how he escaped the army's 1982 attack on the village of Canaque in Santa Maria Nebaja before they burned and destroyed it.
He said he saw the soldiers kill many women who were unable to flee because they were preparing tortilla dough when the army arrived.
"The soldiers tore the victims' hearts out and put them on a little table," Brito said. "They piled them there."
Jose Rodriguez Sanchez, 68, a former high-ranking member of the military chiefs of staff, is also being tried with Rios Montt.
The defence team had delayed the court case with a series of appeals and argued that there was no genocide in Guatemala.
The team also said Rios Montt did not control battlefield operations.
Francisco Garcia Gudiel, one of Rios Montt's lawyers, told the court: "Jose Efrain Rios Montt never gave a written or verbal order to exterminate the Ixils in this country."
The trial was disrupted when Gudiel was expelled after he said Judge Jazmin Barrios was biased against him because they had clashed in previous trials. The three-judge panel rejected his argument and ordered him out of the courtroom.
The defence team tried to get the lawyer for one of Rios Montt's co-defendants to represent Rios Montt.
After a brief and loud argument from that lawyer, the panel finally assigned a third lawyer to represent Rios Montt.
The prosecution says it has no evidence of a direct order from Rios Montt to slaughter civilians during the country's long civil war.
However, the prosecutors hope to prove through a detailed recreation of the military chain of command that Rios Montt must have had knowledge of the massacres of the Ixil and others in the Guatemalan highlands.
Prosecuters alleged Rios Montt's failure to stop the slaughter was proof of his guilt because he held absolute power over the military government.
Rios Montt was protected from prosecution for decades as a congressman by a law that grants immunity to public officials.
Indigenous activists demonstrated outside the court in support of his alleged victims on Tuesday morning.
Former members of government-backed paramilitary groups, blamed for many of the killings, showed their support for the accused.