There are various issues related to Moussaoui case, but I'd now like to take a look at its connection to the Phoenix Memo; new information appeared about this after the Moussaoui trial, as an unredacted version of the DOJ's Office of Inspector General's report into the Bureau's handling of intelligence before 9/11 was released after the Moussaoui trial. It can be found here:
The previous version was heavily redacted and the whole chapter dealing with Moussaoui was absent. Having looked through it now, it seems fairly clear that one of the reasons (perhaps the main reason) that a FISA warrant was not sought to search Moussaoui's belongings (not just his computer), was that knowledge of the Phoenix EC did not circulate at FBI headquarters. When Moussaoui's belongings were searched after 9/11, evidence was found connecting him to two of the hijackers' associates: Ramzi Bin Al Shibh and Yazid Sufaat. It would have been a relatively simple matter to trace the hijackers in the US from Bin Al Shibh based on their phone calls, the fact that they lived with him for years and the surveillance of the Hamburg cell previously carried out by various agencies, including the CIA.