For years, defense lawyers in the Guantánamo cases have spoken of reviewing disturbing government photos of the prisoners being held by the C.I.A. in the Bush administration’s secret overseas prison, the black sites. But they were marked classified, and the world was not allowed to see them. Until now.

Lawyers in the Sept. 11 case have released a single photo taken by the C.I.A. of one prisoner, Ammar al-Baluchi, showing his gaunt, malnourished naked body, circa 2004 at an overseas prison.

The lawyers said the photo, which was first published by the Guardian newspaper, emerged through a classification review process at the military commissions, the war court at Guantánamo Bay, Cuba.

While photos have leaked of U.S. troops abusing prisoners in the aftermath of the attacks of Sept. 11, 2001, including from the Army-run Abu Ghraib prison in Iraq in 2004, none have ever emerged from the C.I.A. black sites. In fact, in 2005 the agency’s leadership destroyed videotapes of interrogations at a black site in Thailand to make sure they were never seen.

This is the kind of material defense lawyers have long sought to present to a judge or jury as evidence of outrageous government conduct, to avert a death penalty or have a war crimes case dismissed.