Mr. Barrientos was taken to court on June 13 by the Center for Justice & Accountability, a San Francisco-based legal advocacy group, and the New York law firm Chadbourne & Parke.

They filed a civil lawsuit against Mr. Barrientos in 2013 on behalf of the Jara family under the Torture Victim Protection Act, designed to hold human rights violators living in the United States accountable.

The day after the coup on Sept. 11, 1973, Mr. Jara was arrested during a military assault at the State Technical University, where he worked, along with hundreds of students and faculty. They were taken to the Chile Stadium, an indoor arena in the capital used as a mass detention center. It was renamed the Víctor Jara Stadium in 2003.

Three days later Mr. Jara’s body, with dozens of bullet wounds, was found outside a cemetery in Santiago along with four other victims. An autopsy of his remains, which were exhumed in 2009, confirmed two gunshots at the back of his head and 44 more wounds all over his body.

A former soldier, José Navarrete, testified that Mr. Barrientos boasted about having shot Mr. Jara twice in the head. “He used to show his pistol and say ‘I killed Víctor Jara with this,’ ” he told the court in a videotaped deposition. Mr. Navarrete said he had not come forward with his testimony before for fear of retaliation.

The whereabouts of Mr. Barrientos were unknown until mid-2012, when a Chilean television crew located him in Florida, where he had moved at the end of the Pinochet dictatorship in 1990. In December 2012 a Chilean judge, Miguel Vásquez, charged Mr. Barrientos in absentia with the murder and requested his extradition.

The defendant’s lawyer, Luis F. Calderon, in his opening statement, described Mr. Barrientos as a hard-working immigrant seeking to “live the American dream.” He said Mr. Barrientos started out working as a landscaper and then became a cook. Mr. Barrientos has worked at Perkins Restaurant in Deltona over the past 10 years. “He is a simple man leading a simple life,” Mr. Calderon said.