“The grave deficiencies or incoherence of the investigation appear to result, in part, from gross incompetence of the services involved in the United Arab Emirates, but also from the moral, pseudoscientific and political prejudices which undoubtedly influenced the inquiry,” the French ambassador to the United Arab Emirates wrote in a confidential cable dated Sept. 6.

Most infuriating to Alex and his mother, Véronique Robert, is that police inaccurately informed French diplomats on Aug. 15, a month after the assault, that the three attackers were disease-free, the diplomats say. Only at the end of August did the family learn that that the 36-year-old assailant was H.I.V. positive. The case file contains a positive H.I.V. test for the convict dated March 26, 2003.

“They lied to us,” Ms. Robert said. “Now the Damocles sword of AIDS hangs over Alex.”

So far the teenager has not tested positive for H.I.V., but he will not know for sure until January, when he gets another blood test six months after the exposure.

A doctor examined Alex the night of the rape, taking swabs of DNA for traces of the rapists’ sperm. He did not take blood tests or examine Alex with a speculum. Then he cleared the room and told Alex: “I know you’re a homosexual. You can admit it to me. I can tell.”

Alex told his father in tears: “I’ve just been raped by three men, and he’s saying I’m a homosexual,” according to interviews with both of them.

The doctor, an Egyptian, wrote in his legal report that he had found no evidence of forced penetration, which Alex’s family says is a false assessment that could hurt the case against the assailants.

In early September, after the family learned about the older attacker’s H.I.V. status and the French government lodged complaints with the United Arab Emirates authorities, the Dubai attorney general’s office assigned a new prosecutor to the case. Only then were forensic tests performed to confirm that sperm from all three attackers had been found in Alex.