A federal court found he was 17, but after a dental exam an asylum seeker is held in California with adults who do not speak his language

First he fled Afghanistan after his father and brother were murdered by the Taliban. Then he flew to Ecuador on what his lawyers described as a forged passport, and eventually he crossed the southern border into the United States, immediately surrendering to authorities. Now Hamid, who a federal court had determined to be a child, is detained in California with hundreds of adult migrants, terrified and alone, and unable to converse with anyone inside the center as he speaks only Pashto.

His lawyers accuse Immigration and Customs Enforcement (Ice) of holding Hamid (not his real name) unlawfully as a dispute over his age leaves him in limbo.

“I’m feeling very upset and nervous,” Hamid said in a translated statement to the Guardian from the Mesa Verde detention center in Bakersfield. “I have cried to my judges many, many times to please put me back with children my own age. My life inside detention is so hard.”

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Hamid fled his village last year after receiving the same threats as his brother after he helped distribute vaccines, according to his lawyers.

The Afghan asylum seeker has maintained since his arrival in the US that he is 17. He was born in the rural district of Achin, near Pakistan, and because he was delivered at home he was never issued a birth certificate. He was, however, issued a tazkera, an Afghan national identity card, when he was 14. His lawyers state that it shows he is 17.

Nonetheless, Hamid was declared an adult by Ice through the use of controversial age determination testing. The form of testing has been branded unreliable by a federal audit and was dismissed as “pseudoscience” by Hamid’s attorneys.

Documents seen by the Guardian show that Hamid was subjected to a dental exam, conducted by a dentist based at the San Antonio School of Dentistry in Texas, that was used to determine his age. The single-page report concludes that an assessment of Hamid’s dental X-rays puts the “empirical statistical probability” of Hamid’s being 18 or over at 79.52%.

The dentist who conducted the assessment, David Senn, did not respond to a request for comment. According to a news report by Reveal, Senn has conducted at least one other age determination test using dental records for Ice in recent months. The Somali asylum seeker he examined was also determined likely to be an adult.

In 2009, the Department of Homeland Security’s inspector general released a report that recognized “radiographs of a person’s bones or teeth ...cannot produce a specific age due to a range of factors affecting an individual’s growth. These include normal biological variation, as well as cultural and ethnic differences. The timing of puberty, diet, genetics, health, and geography can also affect tooth and bone development.”

Ice’s guidelines state that age determination tests, including dental assessments, should only be used as a “last resort” when no other “conclusive information is available” to determine a detainee’s age.

On 23 April, Judge Patrick O’Brien ruled in favour of Hamid in a San Francisco court, finding him to be under the age of 18 and pointing to the government’s overreliance on dental records.

“The respondent’s birth certificate and consistent assertions of being under eighteen outweigh dental age test and his use of a different birth date while traveling to the US,” O’Brien ruled, with reference to Hamid’s tazkera.

But in a twist that has frustrated Hamid’s lawyers, O’Brien revoked his ruling on Monday after homeland security lawyers presented the court with documents obtained from the Afghan government indicating Hamid was over 21.

His lawyers state these are forgeries used to obtain his false passport, which allowed him to flee the country last year. They will continue to fight against the ruling.

“I think Ice are grasping at straws and trying to make an example out of my client to dissuade people like him from coming here and applying for asylum,” said Hamid’s lawyer Mariel Villareal, who is representing the asylum seeker pro bono.

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“The government’s arguments are really weak and any amount of research could help clarify why a child fleeing violence against his family would not be worried about inflated information on an identification document like a passport that allowed him to leave the country.”

It seems likely Hamid will remain in adult detention as his asylum application is processed, despite a sponsor in Texas, a close family friend who had lived in his village in Afghanistan, being willing to take him in if he was granted parole.

In his statement, Hamid said: “I don’t understand what I did to be treated like a criminal and put in jail.”

A spokesman for Ice did not respond to specific questions from the Guardian on Hamid’s case but issued a statement on Friday that said his “true age is a matter that remains the subject of litigation”.

Ice’s statement also made public Hamid’s full name, which the Guardian has chosen not to publish given his asylum application and the continuing dispute over his age.