Why hasn't bin Laden been indicted for 9/11?

Just wondering. A federal grand jury indicted him for terrorist attacks overseas prior to 9/11.
See the indictment at http://wwww.fas.org/irp/news/1998/11/98110602_nlt.html.
One web report quotes an FBI spokesman as saying that bin Laden wasn't listed as a suspect in 9/11 because he hasn't been indicted.
A google search shows up no indictment of bin Laden in 9/11.
So why wasn't he indicted? Either prosecutors thought there was insufficient evidence against him or the feds wanted to avoid drawing attention to their 9/11 investigation deficiencies.
If pressed, however, I'm sure Gonzales et al would claim a trial of bin Laden in absentia would reveal too many dark national security secrets.