Courtesy of Jon Franks

(NEW YORK) -- A U.S. Navy veteran imprisoned in Mexico for more than 13 years for a crime he did not commit is now a free man after a judge overturned his conviction on Wednesday in the city of Acapulco.

"I’m so happy to be out and going home and be reunited with my family and to start my life again. I’m so grateful for my second chance," 46-year-old James Frisvold told ABC News exclusively after he walked free on Thursday from the notorious Las Cruces prison.

Frisvold headed back to his native California, where he was set to be reunited with his mother, sister and uncle at a private airport.

His release was secured by months of unofficial diplomacy orchestrated by Jonathan Franks, a family representative who worked with former New Mexico Gov. Bill Richardson, now head of the Richardson Center for Global Engagement. Both were present when Frisvold left Las Cruces.

"For years, the Frisvolds tried and failed to get the attention of three successive U.S. administrations and repeatedly related his torture and his innocence to the consular agents in Acapulco to no avail," Franks told ABC News on Wednesday. "As a result of this ordeal, Mr. Frisvold hopes to start a conversation with policymakers around how to better address cases like his."

Cases like his -- of an innocent American left to languish in another country's criminal justice system -- are less clear cut than those Americans that the U.S. State Department deems wrongfully detained by rogue regimes who often use them for bargaining chips. But according to Franks, there are far more of them and their cases require intervention, too.

Frisvold had been imprisoned for the 2010 killing of Natalya Sidorova, a Russian citizen married to American Jerry Schultz. Frisvold said in interviews with ABC News that the three of them traveled to Acapulco after Schultz promised Frisvold, an acquaintance, a job when they returned to Sacramento.

But while Schultz and Sidorova were walking down a hall in their hotel, she was brutally attacked by an unknown male assailant, according to surveillance footage obtained by ABC News. The video appears to show Schultz stood by as the man stabbed her repeatedly, and after the killer fled, Schultz went into his hotel room, returned with a bucket of ice and dumped it on her body.

After a bystander noticed the scene, Schultz appeared to call for help, according to the surveillance footage. Court filings reviewed by ABC News show he later identified Frisvold as the assailant, but both men were arrested by local authorities and charged in Sidorova's slaying.

Frisvold admitted to the crime during interrogation, then later said he was tortured and forced to sign a confession that he says was written for him, according to both the court records and what Franks told ABC News.

Frisvold has since maintained his innocence but was stuck in prison for 13 years of complicated proceedings in a language he still doesn't understand. He was first convicted of qualified homicide in 2017, even after a government-employed criminologist testified that Frisvold could not be the man in the surveillance footage because of differences in their skull structure and facial features, according to the court documents.

That conviction was ultimately thrown out in 2019 by a state appeals court, which ruled that Frisvold's rights were violated during the trial. But instead of being released, the local prosecutor retried Frisvold, where a second government-employed criminologist testified in 2019 it could not be he in the surveillance footage of the grisly killing.

Still, the court proceedings stalled, with little movement and no decision in his case.

That finally changed with Wednesday's decision because of weeks of what Richardson's team called "careful and diligent engagement with the appropriate authorities." A local judge found him not guilty and ordered his release. (Authorities say Schultz died in prison in 2015, but no autopsy was ever done.)

During Frisvold's early years in prison, his father, also named James Frisvold, visited multiple times, urging local officials to release him. But the elder Frisvold's efforts failed to attract much initial attention and he died in February 2020 -- a loss that the U.S. Navy veteran still has trouble talking about.

His mother, Mariann Frisvold, was determined not to face the same fate as her husband -- dying without ever hugging their son again. Earlier this year, she hired Franks, who has a background in public relations and has worked with other Americans detained abroad, to take on her son's case after repeatedly sending him messages and emails.

"If he gets out, is it going to be because I read a Twitter message. Is it that arbitrary?" Franks said in an interview earlier this month, during one of three trips to Acapulco and the state capital, Chilpancingo, to lobby local officials on Frisvold's behalf.

Franks worked with the Richardson Center, which has helped secure the freedom of a handful of detained Americans, including Taylor Dudley, another U.S. Navy veteran who was released by Russian authorities in January after what are known as track-two negotiations. Franks previously served as the family representative for imprisoned U.S. veterans including Trevor Reed and Michael White, who were detained by Russia and Iran, respectively.

"This is proof to me that what I've always suspected was true -- that if we could just do boots on the ground where the person is locked up and have a fair chance at making an argument, we could bring home a lot of people. And that's what happened here," Franks said in the earlier interview.

In particular, Franks has blamed the State Department, including its consular office in Acapulco, for not paying greater attention to Frisvold's case.

A State Department spokesperson told ABC News that they are "aware" of Frisvold's release but offered no further comment.

ABC News will have much more exclusive coverage of Frisvold's case after embedding with the effort to free him. Tune into ABC's "Nightline" and ABC News Live Prime for more.

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