According to reports, we first started tracking the couriers who would ultimately lead us to Osama bin Laden over four years ago.

The stream of information that led to Sunday’s raid began over four years ago, when U.S. intelligence personnel were alerted about two couriers who were working with al Qaeda and had deep connections to top al Qaeda officials. Prisoners in U.S. custody flagged these two couriers as individuals who might have been helping bin Laden, one official said

“One courier in particular had our constant attention,” the official said. He declined to give that courier’s name but said he was a protégé of Khalid Sheikh Mohammed and a “trusted assistant” of Abu Faraj al-Libbi, a former senior al Qaeda officer who was captured in 2005.

“Detainees also identified this man as one of the few couriers trusted by bin Laden,” the official said. The U.S. intelligence community uncovered the identity of this courier four years ago, and two years ago, the U.S. discovered the area of Pakistan this courier and his brother were working in.

In August 2010, the intelligence agencies found the exact compound where this courier was living, in Abbottabad, Pakistan. The neighborhood is affluent and many retired Pakistani military officials live there.

The reference to Abu Faraj al-Libi is notable in this context for two reasons. He was one of the last High Value Detainees picked up. The Red Cross dates his capture to May 2, 2005 (though he appears to have been held in joint Pakistani-US custody for a time and his Detainee Assessment Brief says he was transferred to US custody on June 6, 2005), and of the HVDs moved to Gitmo in September 2006, he was the last to be picked up.

More interesting, though, are some details from his DAB. In 2003, OBL assigned al-Libi to be “the official messenger” between himself and others in Pakistan. And, apparently at that point, al-Libi moved with his family to Abbottabad, the city where OBL was found.

In July 2003, detainee received a letter from UBL’s designated courier, Maulawi Abd al-Khaliq Jan, requesting detainee take on the responsibility of collecting donations, organizing travel, and distributing funds to families in Pakistan. UBL stated detainee would be the official messenger between UBL and others in Pakistan.12 In mid-2003, detainee moved his family to Abbottabad, PK and worked between Abbottabad and Peshawar.13

His DAB describes al-Libi providing intelligence on al Qaeda’s courier system.

Detainee reported on al-Qaida’s methods for choosing and employing couriers, as well preferred communication means.

And in May 2005 (when the Red Cross says he was captured), al-Libi said he was responsible for facilitating al Qaeda in “settled areas of Pakistan.”

In TD-314/37025-05, detainee stated of early May 2005, he was responsible for facilitation within the settled areas of Pakistan, communication with UBL and external links.

That all sounds suspiciously like the kind of portfolio that might include arranging for a custom-built mansion in Abbottabad for OBL’s family.

None of this means, of course, that al-Libi is the HVD who first IDed the courier who ultimately led to OBL. But it does seem like he was a likely source of that information.