WASHINGTON -- Confined to the basement of a CIA secret prison in Romania about a decade ago, Khalid Sheikh Mohammed, the admitted mastermind of the 9/11 terrorist attacks, asked his jailers whether he could embark on an unusual project: Would the spy agency allow Mr. Mohammed, who had earned his bachelor's in mechanical engineering, to design a vacuum cleaner?
The agency officer in charge of the prison called CIA headquarters, and a manager approved the request, a former senior CIA official said in an interview.
Mr. Mohammed had endured the most brutal of harsh CIA interrogation methods and confessed to a career of atrocities. But the agency had no long-term plan for him. Someday, he might prove useful again or perhaps even stand trial. And for that, he would need to be sane.
"We didn't want them to go nuts," said the former senior CIA official, one of several who spoke on condition of anonymity because they weren't authorized to discuss now-shuttered CIA prisons or Mr. Mohammed's interest in vacuums.
So, using schematics from the Internet as his guide, Mr. Mohammed began re-engineering one of the most mundane of household appliances. That the CIA may be in possession of the world's most highly classified vacuum cleaner blueprints is but one peculiar, lasting byproduct of the controversial U.S. detention and interrogation program.
By the CIA's own account, the program's methods were "designed to psychologically 'dislocate' " people. But once interrogations stopped, the agency had to try to undo psychological damage inflicted on detainees. In Romania, the prison provided detainees books to read. Mr. Mohammed, former officials said, enjoyed the Harry Potter series. The CIA apparently succeeded in keeping him sane; military records show he appears to be in good health.
Others haven't fared as well. Accused al-Qaida terrorists Ramzi Binalshibh and Abd al-Nashiri, also locked up in Poland and Romania, have mental issues. Mr. Nashiri suffers from depression and post-traumatic stress disorder. Mr. Binalshibh is treated for schizophrenia.
Mr. Mohammed was subjected to harsh interrogations in Poland. Agency officers and contractors forced him to stay awake for 180 hours, according to a CIA inspector general's report. He also underwent 183 instances of waterboarding, or simulated drowning. After the CIA prison in Poland was shut in September 2003, he was moved to Bucharest, a black site code-named "Britelite." The CIA soon sought ways to entertain him as his intelligence value diminished.
The prison had a debriefing room, where Mr. Mohammed, who saw himself as something of a professor, held "office hours," as he told CIA officers. While chained to the floor, he would lecture CIA officers on his path to jihad, his childhood and family. Tea and cookies were served.
Along with the other five Bucharest prison detainees, Mr. Mohammed was given assignments about his al-Qaida knowledge, or "homework," as CIA officers called it. He was given candy bar rewards for his studiousness.
Though Mr. Mohammed enjoyed Harry Potter books, they were a source of frustration for CIA officers at the prison. For security reasons, after a prisoner finished a book, they tediously checked each page to be sure detainees weren't passing messages. They once caught detainees trying to hide a warning not to discuss Osama bin Laden's courier. The courier later led the CIA to the al-Qaida leader's Pakistan compound, where U.S. Navy SEALs killed him in 2011.
Mr. Mohammed graduated from North Carolina A&T State University in 1986 with a mechanical engineering degree. It is unclear whether he was interested in designing a better vacuum or had ulterior motives.
It remains a mystery how far Mr. Mohammed got with his designs, or whether they still exist.