Despite such misgivings about wartime polygraph testing, the U.S. government also authorized the use of handheld devices in Iraq and Afghanistan that were considered even less reliable than the traditional machines were. The documents don’t say what type of equipment the Air Force used, and the government had redacted portions of the documents. Katelyn Sack, a University of Virginia polygraph researcher who provided the documents to McClatchy, said the Air Force appeared to have used traditional machines.

One of the polygraphers worried that military personnel were falsely implicating people. In one case, interrogators claimed that a detainee was arrested with a “large cache of weapons.” It turned out that the man lived in a neighborhood where several people were rounded up.

“The ‘weapons cache’ was either an accumulation of weapons found in all the homes, or was found in one of the homes but attributed to each of the individuals detained at the same time,” the polygrapher wrote. “The interrogator told me that these ambiguous reports are not unusual. . . . He told me that it could very well be that this particular detainee didn’t have any weapons at all in his home.”

One polygrapher – who screened 110 detainees in 2005 and 2006, including at Abu Ghraib – said the polygraph test results had no impact on detainees at Abu Ghraib because interrogators “already knew” from other evidence that the detainees were guilty.

“Interrogators wanted to use the failed polygraph (what they suspected would be a failed polygraph) as a ‘hammer,’ ” the polygrapher wrote.

Another polygrapher said a test “ ‘cleared’ an old man . . .wrongly ‘fingered’ by a jealous neighbor.”

“Despite the results he was sent to Abu Ghraib prison,” the polygrapher said.

In an internal memo, the Air Force said 46 percent of the detainees were deemed to have been lying. Yet 90 percent of the tests were based on “extremely generic, anonymous and perishable reporting,” according to the memo.

One polygrapher said the interrogators sometimes told the detainees they’d failed when they had not.

But the Air Force pressed ahead and temporarily authorized a controversial technique that intelligence agencies use during polygraph testing. The Air Force said in the memo that the technique, known as the relevant/irrelevant test, was used with “great success” in Afghanistan. But some Air Force polygraphers in Iraq raised questions about it.

The technique, which the National Security Agency uses, often shows people as being deceptive, known as “DI,” according to one polygrapher. The NSA also sent polygraphers to Iraq, the documents show.

“I felt as if I were unfairly administering a ‘DI’ test to an individual who might actually” not be lying, an Air Force polygrapher wrote. Unlike the Air Force results, the National Security Agency tests on detainees in Iraq “are not reviewed by anyone, are not sent forward to their headquarters and are not filed in any database,” another polygrapher wrote.