Climbing the stairs to the second floor, Mr. Qadir passed a body outline that marked the spot where Bin Laden’s 22-year-old son, Khalid, was shot dead. Then he turned to a small room with a low ceiling, an empty wardrobe and a tight cluster of bullets holes in one wall, he said. Above that, on the ceiling, was a fading splash of blood that, his Pakistani intelligence escort told him, belonged to Bin Laden.

“As a former soldier, I was struck by how badly the house was defended,” Mr. Qadir said in an interview. “No proper security measures, nothing high-tech — in fact, nothing like you would expect.”…

Mr. Qadir claims that Bin Laden’s fifth and youngest wife, Amal Ahmed al-Sadah, told Pakistani interrogators that her husband underwent a kidney transplant operation in 2002 — a claim that, if proven, could help explain how the ailing Saudi militant was able to survive with a known kidney ailment, but raises questions about who was helping him. He also heard of poisonous mistrust between Bin Laden’s wives. In the cramped Abbottabad house, he was told, tensions erupted between Ms. Sadah, described as “the favored wife,” and Khairiah Saber, an older woman who occupied a separate floor. In interrogation, Ms. Sadah accused her rival of having betrayed their husband to American intelligence.

Bin Laden’s youngest wife also told interrogators that her husband shaved his beard and disguised himself as an ailing Pashtun elder as he leapfrogged between safe houses across northwestern Pakistan, eventually regrowing the beard after finally settling in the Abbottabad house in 2005.