LONDON  A British judge has ordered a hearing into whether the British government must turn over evidence bearing on accusations by a prisoner at Guantánamo Bay, Cuba, that he was tortured during interrogation in Morocco.

The judge, acting on a request by lawyers for the prisoner, Binyam Mohamed, rejected an argument of the British government that releasing any documents risked “that more robust evidence of mistreatment of C.I.A. prisoners could emerge in the future.”

The British government, in a court filing last month, accepted that Mr. Mohamed had presented an “arguable case” that he had been tortured after his “extraordinary rendition” to Morocco and Afghanistan. Mr. Mohamed has said that, among other things, his interrogators in Morocco made cuts on his chest and genitals with a razor.

To support Mr. Mohamed’s claim, his lawyer Clive Stafford Smith is seeking photographs that he said an American soldier took of Mr. Mohamed’s injuries, during a flight from Morocco to Cuba.