A Russian court ruled that a Ukrainian boy who claims he’s 13 be tried as an adult based on the size of his penis, according to The Moscow Times. Tomas, whose last name was not released to protect his identity, was arrested on suspicion of stealing a cellphone in March—an accusation he denies.

The teen had moved to Moscow that same month to live with his aunt. His family claims he was 12 at the time of the arrest and has produced Ukrainian documentation that he used to cross the Russian border as proof. But authorities think he is older and ordered a medical examination to determine his real age. Based on the size of his penis and teeth, prison doctors told the court they believe he is actually 16 or 17.

It’s an important distinction. Individuals 16 and over can be tried as adults in Russia, and that age comes down to 14 in the case of more serious crimes like rape and murder. As a result, Tomas has since been sentenced as an adult and was sent to jail. His family has challenged the ruling, and the regional prison service has agreed to review his case.