An American teacher was jailed for child abuse in China in 2014. He still says he's innocent — if only anyone would listen.

Updated 0059 GMT (0859 HKT) June 9, 2021

Hong KongDavid McMahon hated the design of his classroom.

Located on the ground floor of the Pudong campus of the Shanghai French School, its almost floor-to-ceiling windows made him feel like he was "teaching in aquarium," in the words of one of McMahon's colleagues. Passersby couldn't help but look in, and their attention would inevitably distract the kindergarteners inside.
But when, in 2013, he was accused of abusing several of his students, the windows suddenly seemed to McMahon and his defenders a saving grace -- proof the claims being made against him could not have happened. How could he have molested multiple children over the course of months, his lawyers planned to ask in court, in full view of anyone walking through a heavily-trafficked area of the campus?
It was one of many strands of a defense that seemed relatively iron tight to McMahon and his fiancée Linnea, who said that while they were appalled and upset at the charges, they weren't overly worried, figuring the truth would come out at trial.
"At the beginning it just seemed like this couldn't possibly go any further, there wasn't enough evidence, like how could this happen?" said Linnea, who requested to be identified only by her first name in order to protect her privacy.
But when McMahon's case came to court, just one of McMahon's witnesses was allowed to testify, and she was only permitted to speak to his character. Almost all the evidence put forward by his lawyers was summarily dismissed, court documents show, demonstrative of the difficulties defense teams often have in the Chinese justice system, where around 99% of prosecutions end in a guilty verdict.
On July 2, 2014, McMahon was found guilty of child molestation and sentenced to 12 years in prison.
To this day, McMahon maintains he is innocent of all charges against him, despite what supporters say is ongoing pressure from the Chinese authorities to sign a confession, which could bring a reduction in his sentence and better treatment while in prison.
No physical or forensic evidence was ever presented to tie McMahon to the crime, with the case relying solely on the testimony of very young children. Claims that their testimony may have been flawed were dismissed by the court, as was the suggestion testimony may have been inappropriately influenced by parents or police.
CNN has interviewed over a dozen people involved in the case, including former colleagues of McMahon's and parents at the school where he taught, and reviewed Chinese and US court documents, witness statements, US State Department records, and communications sent by McMahon and his accusers ahead of the trial.
None of McMahon's accusers responded to requests for comment. In a statement, the Lycée Français de Shanghai said it had "no comment to make."
Prosecutors and police in Shanghai also did not respond. Previously, Chinese officials have stated that the country's "judicial authorities handle cases involving criminals of different nationalities in accordance with law" and that "every criminal is equal in the application of the law."
Since he was first arrested, McMahon's family and friends have attempted to get US officials and lawmakers to lobby on his behalf, with little success. Media coverage has been limited to a handful of stories around the time he was charged, largely repeating what was put out by Shanghai prosecutors.
Thanks to years of work behind the scenes, however, this has gradually begun to change. McMahon's case has recently been taken up by the James Foley Foundation, which advocates on behalf of Americans detained overseas.
In a statement to CNN, Executive Director Margaux Ewen said that "based on the evidence we've seen from many sources," including FBI agents and US State Department officials, the Foundation believes "David is innocent of the charges against him."
"We hope the United States government will be helpful in securing his release and repatriation home to the US," Ewen said.
Rob Saale, a former FBI Special Agent and director of the US Hostage Recovery Fusion Cell, who sits on the Foley Foundation's advisory council, said that on examining the case "there were a number of factors that caused me to believe that David's conviction was suspect."
"What was most troubling was the process for the interviewing of the victims of the case," Saale said, adding that "some of the allegations seemed far fetched," and did not line up with other testimony or evidence.