Abdelbaset al-Megrahi was convicted in the bombing of Pan Am Flight 103, which crashed onto the Scottish town of Lockerbie on Dec. 21, 1988. A total of 270 people died in the attack.
Doctors prior to his release in 2009 said Megrahi had around three months to live because of a prostate cancer prognosis.
George Burgess, a government lawyer who advised Scottish Justice Minister Kenny MacAskill, said the three-month figure was given as the median survival rate for patients with Megrahi's type of cancer, The Herald (Glasgow) reports.
Three months was cited by Scottish officials as the benchmark for a prisoner release on compassionate grounds. The Megrahi release earned the ire of U.S. lawmakers, who expressed outrage over his case after the BP oil spill in the Gulf of Mexico, which came nearly a year after the release.
U.S. Sen. Robert Menendez, D-N.J, who led an investigation into Megrahi, said after his September visit to Edinburgh that the decision to release the Libyan intelligence officer was "manipulated" and somehow linked to a BP oil deal with Tripoli.
Scottish officials said the three-month estimate was likely a "shot in the dark," The Herald reports, adding that key advisers to MacAskill recognized the prognosis as "an estimate."
Libyan authorities said Megrahi, now free in Libya, could live another 10 years.