Taped lectures feature prominent professors, most notably Arthur R. Miller of Harvard Law School.
Professors tape lectures on everything from Greek philosophy to physics.
Taped lectures, though, do not allow students to interact with the professors.
"On the face of it, taped lectures should be boring," Mr. Anderson said.
A search of Khalid's apartment uncovered a large amount of extremist literature in the form of taped lectures by radical clerics and books, the jury was told.
"She thought it was great," Ms. Swenson said, "that she was able to take a calculator to college or a cassette player to tape lectures".
He also joined Abdullah Azzam, whose taped lectures had influenced him at the university, in forming Makhtab al Khadimat, a group that recruited and trained Muslim volunteers from Egypt, Algeria and other countries to fight in the Afghan war.
A series of taped lectures — given at Harvard in 1967 but only recently transcribed — display the eloquence and erudite, offhand wit familiar from his writings as well as a charming, plainspoken modesty.
He also listened to taped lectures of an influential teacher, Abdullah Azzam, a Palestinian major figure in the Muslim Brotherhood, which is dedicated to resurgent Islamic faith, and the experience deepened Mr. bin Laden's religious commitment.
Accordingly, a number of the young men arrived in America armed with cassettes of taped lectures from their elders, warning of the myriad dangers they perceived in the boys' future.
