Samit told MacMahon he couldn't persuade FBI headquarters or the Justice Department to take his fears seriously. No one from Washington called Samit to say this intelligence altered the picture the agent had been painting since Aug. 18 in a running battle with [FBI Agent Mike] Maltbie and Maltbie's boss, David Frasca, chief of the radical fundamentalist unit at headquarters. They fought over Samit's desire for a warrant to search Moussaoui's computer and belongings. Maltbie and Frasca said Samit had not established a link between Moussaoui and terrorists.

....Under questioning from MacMahon, Samit acknowledged that he had told the Justice Department inspector general that "obstructionism, criminal negligence and careerism" on the part of FBI headquarters officials had prevented him from getting a warrant that would have revealed more about Moussaoui's associates. He said that opposition blocked "a serious opportunity to stop the 9/11 attacks."

In order to win the death case, the Goverment must prove that Moussaoui's lies contributed to the death of at least one person killed in the 9/11 attacks.

The FBI's actions between Moussaoui's arrest, in Minnesota on immigration violations on Aug. 16, 2001, and Sept. 11, 2001, are crucial to his trial because prosecutors allege that Moussaoui's lies prevented the FBI from discovering the identities of 9/11 hijackers and the Federal Aviation Administration from taking airport security steps.

Perhaps most damaging of all to the Government's case:

MacMahon introduced an Aug. 31 letter Samit drafted "to advise the FAA of a potential threat to security of commercial aircraft" from whomever Moussaoui was conspiring with. But Maltbie barred him from sending it to FAA headquarters, saying he would handle that, Samit testified. The agent added that he did tell FAA officials in Minneapolis of his suspicions.