CAIRO — Lawyers for an American held prisoner in Yemen’s capital said that their client could be sentenced to death on murder charges at his next hearing scheduled for Wednesday, despite the difficulty of conducting a trial during Yemen’s civil war.

The prisoner, Sharif Mobley, who is from New Jersey, was allowed to make a rare phone call late last month to his lawyers in London telling them that the prison where he was being held in Sana, the capital, had been hit by airstrikes and that he had been repeatedly beaten in custody.

Mr. Mobley was brought before a judge in October without a lawyer and told that a verdict could be passed at his next court hearing.

“They’re going to make a ruling without me being able to defend myself,” Mr. Mobley told his lawyers at Reprieve, an international human rights organization, according to a recording of the call provided by the group. Namir Shabibi, an investigator at Reprieve, said on Monday that the group had found a local lawyer to represent Mr. Mobley at his next hearing, but that they were still concerned that the judge could move directly to sentencing their client without a trial.