In this article, Gareth Porter quotes Thomas Fingar several times about the 2007 NIE on Iran’s nuclear weapons program. Fingar provides a few insights into the process of creating such an estimate:

… a draft completed in June 2007, after several months of work, simply reaffirmed the main conclusions of the 2005 estimate, according to Fingar. In testimony in early July before the House Armed Services Committee, Fingar actually restated, word for word, the primary conclusion of the 2005 NIE: “We assess that Tehran is determined to develop nuclear weapons, despite its international obligations and international pressure.”

That draft conclusion reflected what Fingar called “the deference that was paid to prior judgments.” Previous NIE’s “damn near came to be sacred texts,” he said. “To go back and redo, relook at original information and judgment reached earlier — it simply wasn’t done.”

Fingar also provides a detail about the dissent which appears in the 2007 NIE:

[Fingar] said that he had personally dissented from the NIE’s “high confidence” that Iran had “halted its nuclear weapons program” in 2003. “The dissent,” he explained to me, “was on the level of confidence that the halt had embraced all aspects of the program. I did not think we had enough specific information to have high confidence that it did.“