The United States closed its embassy in Yemen for security reasons on February 10, evacuating its staff at dawn under the cover of drones and warplanes. But they left one young American behind: my client Sharif Mobley, a 30-year-old father of three from New Jersey.

It’s possible that Sharif was woken in his prison cell by the sound of those planes flying over the city. Perhaps a guard even told him in the night that his own government had left, and he was now utterly alone. I can’t say, because Sharif went missing a year ago today, and no one – Yemeni or American – will tell me where he is so I can go ask him myself.

Related: Sharif Mobley: US citizen lost in Yemeni prison system left behind in Sana'a

Colleagues of mine last saw him on February 27, 2014, through a fence in Sana’a’s Central Prison. Reprieve is defending Sharif in a criminal case in Yemen – but the judicial system lies in tatters with the rest of the state. Last year at least seven hearings passed without Sharif being brought to court, with no explanation from the government. Our repeated attempts to knock on prison doors have been rebuffed. Now, with the country in turmoil, the courts have simply closed.

Today, Sharif is incommunicado, alone, staring down the barrel of a capital charge in a hopelessly unfair court process. This sorry tale begins in January 2010. At that time Sharif was living with his wife and kids in the Yemeni capital Sana’a, and had gone to the US Embassy seeking a passport for his newborn son so the family could head home to the States. But FBI agents put a hold on the family’s papers and shook Sharif down for information instead.

The FBI never saw fit to arrest Sharif. Why bother, they seem to have thought, when they could choose the simpler expedient of having a US citizen kidnapped at gunpoint and ‘softened up’ for questioning?

On the morning of January 26, 2010, as Sharif was standing outside his local shop, a van drew up alongside him. Masked men jumped out, shot him in the leg, and threw him in the back of the van.

My client then vanished from the face of the earth. We now know – thanks to documents released under Freedom of Information ACT litigation – that he was being interrogated by US and Yemeni agents in a secret wing of a Sana’a’a hospital. Sharif’s pleas to contact a lawyer or a family member were denied. “You’re not under arrest, son” the agents smirked. “There are no Constitutional rights in Yemen”. They threatened Sharif with beatings and rape in Yemeni jails. A Yemeni dangled the keys to Sharif’s house in his face, and said his wife could look forward to the same.

The agents then made good on some of their threats. The FBI allowed Yemeni guards, in moving Sharif to another black site, to beat Sharif so badly that he had to be hospitalized. Further weeks passed with Sharif held in secret. The prosecution in Sharif’s case alleges that Sharif sought to escape from that second hospital, killing a guard in the process.

The US suggests it has provided appropriate consular assistance to Sharif Mobley, but this is false. Emails between the deputy Consul in Yemen and Washington State Department staff at the time reveal the US authorities’ real attitude to Sharif. One particularly chilling exchange reads:

“Word has it that he may be ending up in the spirit world pretty quickly”.

“Not doing well recovering from his wounds?”

“… more like a quick trial, appeal, and carry out the sentence...”

The typical sentence for a capital case in Yemen is to be brought to a public square and shot through the heart.

Sharif’s Yemeni court file admits none of this history. It begins at the date of the supposed ‘escape attempt’ but offers no answers to the obvious questions: why was Sharif in that hospital room in the first place? Why would anyone seek to flee a hospital?

For a moment last year, it seemed as if a Yemeni judge might actually seek out the truth of all this. Reprieve had requested the court to investigate Sharif’s disappearance – to determine the US’ role in the kidnapping – and was preparing to file the evidence from our FOIA litigation with the Yemeni court. But we were too late. On the eve of our hearing the authorities disappeared Sharif a second time – one year ago today.

A Yemeni security source recently told NBC News that Sharif was shipped to secret detention in coordination with the US, and that American officials are participating in his interrogation. The US Embassy knows where Sharif is held today. Consul staff have visited him, including once on the very day that Reprieve called at the prison where he is most likely to be, and were turned away “for security reasons”. Yet the US refuses to tell Sharif’s family or his legal team where he is.

The State Department has reached for every excuse under the sun to justify this. On one occasion, staffers told Sharif’s wife that the secrecy was “for Sharif’s own safety”. On another memorable occasion, a diplomat replied to my demands for basic information by saying that he had to “respect the privacy of all American citizens”.

The Yemeni legal system can no longer be said to exist and the US Embassy deems Sana’a too dangerous for its own staff. The State Department should be getting Sharif home safe to his family.

Numerous press reports talk of embassy staffers destroying documents in the days leading up to their flight from Sana’a. I wonder whether Sharif’s file was also put into the shredder. It would not surprise me; the intention to cover up US involvement in the case is abundantly clear.

As the embassy SUVs sped out of town towards the airport, they will have passed the grim prison where I suspect Sharif is held. I wonder if anyone looked back.