Why did Helgerson recuse himself from the KSM part of the CIA OIG investigation?

[KJF]

CIA inspector general John Helgerson recused himself from part of the office of inspector general's investigation - the part concerning Khalid Shaikh Mohammed (KSM). This was apparently due to a "conflict of interest" according to the executive summary of the CIA OIG report. What conflict of interests?

He must have been involved in the issue before 9/11, but in what position?

It says here:
https://www.cia.gov/news-information/press-releases-statements/press-release-archive-2001/pr08032001.html

that he was deputy director of national imagery and mapping from March 2000 to August 2001, so it must be something before that.

Here is a brief career history until 1993:
https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/books-and-monographs/cia-briefings-of-presidential-candidates/blurb.htm

Something between 1993 and 2000, then.