The secret document described Prisoner 269, Mohammed el-Gharani, as the very incarnation of a terrorist threat: “an al Qaeda suicide operative” with links to a London cell and ties to senior plotters of international havoc.

But there was more to the story, as there so often is at the Guantánamo Bay prison in Cuba. Eight months after that newly disclosed assessment of Mr. Gharani was written by military intelligence officials, a federal judge examined the secret evidence. Saying that it was “plagued with internal inconsistencies” and largely based on the word of two other Guantánamo detainees whose reliability was in question, he ruled in January 2009 that Mr. Gharani should be released. The Obama administration sent him to Chad about five months later.