Thirty-eight years after he lost his mother, five siblings, and five nieces and nephews during El Salvador’s brutal civil war, Santos Alvaro Pereira still breaks down in tears when he recalls their murder.

Pereira’s relatives were among nearly 1,000 civilians – including 533 children – who were slaughtered by US-trained troops in and around the village of El Mozote in December 1981.

Eighteen former army officers now face trial for crimes against humanity and other charges related to the massacre.

This week, the memory of El Mozote – and the legacy of US cold war-era intervention in Central America – was evoked in Washington DC as the Democratic representative Ilhan Omar grilled Donald Trump’s special envoy to Venezuela, Elliott Abrams, about US policies in Latin America.

But for survivors of the massacre, the pain has never gone away.

On Thursday, Pereira, 59, had hoped to finally learn the whereabouts of his sister Maria, her husband, and their five children – murdered at the ages of 10, nine, seven, five, and three – when forensic experts investigated a potential mass grave at the village.

A court had ordered the exhumation after a local resident, Florentín Ramos, 26, and his father noticed children’s clothes and bone fragments in the topsoil when they went to plant cacao trees.

As the team of anthropologists sifted through the dirt on a hillside outside the village, Pereira said through sobs that he still hoped to give his relatives a proper burial.

But after about an hour, the Argentinian forensic expert Silvana Turner, who led the exhumation, said that bones at the site were not human.

Pereira hardened when he heard that the day would bring no answers. “We have to keep looking,” he said.

“We want justice.”

The massacre came in the early stages of a civil war between leftwing rebels and the US-backed government that eventually claimed 75,000 lives – most at the hands of state forces, according to a United Nations truth commission.

At El Mozote, soldiers from the Atlacatl Battalion – an elite counterinsurgency unit trained, armed, and funded by the US – lined up, interrogated, tortured, and executed villagers. They started with the men before turning to the women and children, gang-raping women and girls.

A forensic team sets a sign to identify the potential gravesite. Photograph: José Cabezas/Reuters

The army also burned houses and crops as part of a “scorched earth” campaign against guerrilla strongholds, where all villagers were suspected of collaborating with the rebels.

An amnesty law passed shortly after the 1992 peace deal shielded the perpetrators from prosecution for more than two decades. The supreme court declared the blanket amnesty unconstitutional in 2016, opening the door to bring civil war-era human rights crimes to trial. El Mozote now serves as a test case.

“[The trial] could transform Salvadoran society by saying that crimes against humanity and grave violations are human rights will not go unpunished,” said El Salvador’s deputy human rights ombudsperson, Carlos Rodriguez, standing beside the exhumation site. “This would send an important message to current and future governments.”

The trial is also likely to cast a spotlight on the US role in the conflict, at a time when Abrams was assistant secretary of state for human rights.

After El Mozote, Abrams dismissed reports of a massacre as a propaganda ploy by leftist rebels and their allies in human rights groups. In a 1982 Senate foreign relations committee hearing, Abrams claimed reports of the death toll were “not credible”.

On Wednesday, Omar noted that Abrams had once described US policy in El Salvador as a “fabulous achievement”.

“From the day that President Duarte was elected in a free election, to this day, El Salvador has been a democracy,” he responded. “That’s a fabulous achievement.”

The CIA poured nearly $1m into President José Napoleón Duarte’s 1984 presidential campaign as part of an effort to block a victory for the far-right military strongman Roberto d’Aubuisson.

Elliott Abrams faced questioning over the US’s past El Salvador policies on Capitol Hill. Photograph: Jim Lo Scalzo/EPA

The Reagan administration hailed Duarte as a centrist reformer who would bring democracy to El Salvador. With Duarte in power, the US increased military aid to El Salvador, hitting a high of $197m in 1984.

But Washington turned a blind eye to the human rights abuses carried out by the military and allied death squads under Duarte’s watch.

For many, justice for El Mozote means seeing state agents pay for their crimes.

“There are indications that high ranking military officers were the ones who planned, executed, and developed [the military operation],” Wilfredo Medrano, a co-prosecutor representing the victims, told the Guardian.

Medrano added the US had a “moral and economic responsibility” to support El Salvador’s search for truth and justice given its historic role backing state abuses.

“Something very important is that [the victims] can find out why, how, and where their family members were killed,” Judge Jorge Guzman, overseeing the case, told the Guardian. “They have a right to reparations for the harm they suffered, both material and psychological.”

