This arc stretched 45 years. But four months ago, the Chilean judge, Miguel Vázquez, sentenced each of eight retired military officers to prison terms of 15 years and a day for the murders of Mr. Jara and of a former prisons director, Littré Quiroga Carvajal. A ninth man received a five-year sentence for helping cover up the crimes.

And in Florida another former officer, who found refuge in the United States, has been declared liable in a civil suit brought by Jara family members, and ordered to pay them $28 million in damages. A court in Chile has asked for the extradition of this man, Pedro Pablo Barrientos Nuñez, but the request remains unfulfilled. Mr. Barrientos, 69, remains at liberty in Florida, where he insisted to Retro Report that he was innocent of wrongdoing and felt “like a victim of political persecution.” Still, the arc may not be done bending.

Víctor Jara grew up poor, and made his own way from age 15. At one point, he studied for the priesthood, but lost interest amid a political awakening that steered him decidedly leftward. He gravitated toward theater and music, becoming part of a movement known as nueva canción, or new song, which infused traditional Latin American folk music with politically and socially inspired lyrics. “Song has great power to create awareness in the face of today’s challenges,” he said.

His activism, popularity and ardent support of the Allende government made him a marked man once the military seized power on Sept. 11, 1973. The next day, soldiers rounded up students and professors at State Technical University in Santiago, where Mr. Jara had taught theater. He and hundreds of others were led to the indoor Chile Stadium (renamed Víctor Jara Stadium in 2003).

He was quickly recognized and taken to the bowels of the arena, there to be tortured. Soldiers crushed his fingers with their rifle butts, and told him mockingly that he would never play the guitar again.

Testimony in the Florida civil case revealed that an officer identified by several witnesses as Lieutenant Barrientos was a commander at the stadium and was giving orders while Mr. Jara was held there. Several days later, the singer’s corpse was found, along with those of several others, dumped outside a Santiago cemetery. He had been shot twice in the head and 44 more times elsewhere. His wife, Joan, a British-born dance instructor, managed to recover the body and bury it. Then she fled to Britain with her young daughters, Amanda and Manuela, and did not return to Chile for a dozen years.

“I am one of the lucky ones” Joan Jara, 91, told Sean Mattison, director of the Retro Report video. “So many people here in Chile, so many families, they still don’t know the destiny of their loved ones. That is the worst fate.”

In death even more than in life, Mr. Jara became an iconic figure for artists around the world who found him a source of political and cultural inspiration. Bruce Springsteen gave a concert in Santiago in 2013, on the 40th anniversary of the military coup, and sang “Manifiesto,” a song that Mr. Jara himself did not live long enough to perform in public. “It’s a gift to be here,” Mr. Springsteen said to the audience, “and I take it with humbleness.”

The rock group U2 wrote a number, “One Tree Hill,” that included this verse:

Jara sang, his song a weapon

In the hands of love

You know his blood still cries

From the ground

Now, graying men have been ordered to prison for their role in the murder. A lingering question is whether Mr. Barrientos will someday join them. Court requests for his extradition have not yet translated into action. As for the civil verdict against him, reached by a federal jury in 2016, it has moral significance but scant practicability. Mr. Barrientos, who made ends meet in Florida as a cook in a fast-food restaurant, would seem in no position to pay a multimillion-dollar judgment.

He left Chile in 1989 and became a United States citizen through marriage in 2010. He lives in a modest two-bedroom house in Deltona, about 30 miles north of Orlando. “I came here looking for the American dream,” he told Mr. Mattison, “and I had it until this nightmare started.”

He might want to keep looking over his shoulder. His failure to disclose his military background when he applied for citizenship could end up as a strike against him. He also may want to keep the name Jakiw Palij in mind.

Mr. Palij, born in a town that was then in Poland and is now in Ukraine, migrated to America after World War II and became a citizen in 1957, settling into a quiet life in Queens. Years later, it was discovered that he had lied in his immigration papers about having been a guard at a Nazi forced labor camp in occupied Poland. In 2003, he was stripped of his American citizenship. Deporting him took years, but in August, justice finally had its day. Mr. Palij, ailing and strapped to a stretcher, was put aboard a plane and packed off to Germany.

He is 95 years old. He should serve as an object lesson for Mr. Barrientos: Old age is not a guarantee against the arc of the moral universe.

My song is not for fleeting praise

nor to gain foreign fame,

it is for this narrow country

to the very depth of the earth.

CLYDE HABERMAN, a regular contributor to Retro Report, has been a reporter, columnist and editorial writer for The New York Times, where he spent nearly 13 years based in Tokyo, Rome and Jerusalem. Subscribe to our newsletter here and follow us on Twitter @RetroReport.

This article first appeared in The New York Times.