If nothing else, the long trial of confessed Al Qaeda member Zacarias Moussaoui - now in its final phase - may have highlighted the difficulties of prosecuting big terrorism cases in a democratic nation's civilian courts.
Mr. Moussaoui himself has been disruptive and belligerent. He's been thrown out of court for outbursts, such as shouting "I am Al Qaeda!" in front of prospective jurors. The courts have struggled with his attempts to serve as his own lawyer, and requests for testimony from other terror suspects.
But the US isn't alone in this regard. In Spain, prosecutors have asked the Supreme Court to review the only conviction thus far directly related to the September 11 attacks. They're no longer sure evidence proves that Syrian-born Spaniard Immad Yarkas provided logistics for the 9/11 conspiracy.
These troubles mean that terrorist prosecutions should be pursued carefully, say some analysts. They don't mean that they shouldn't be pursued at all.
"This is about whether the criminal justice system has any role in the war on terror," says Juliette Kayyem, a public policy expert at Harvard's John F. Kennedy School of Government.
Last April, Moussaoui pleaded guilty to being part of a broad Al Qaeda conspiracy to fly airplanes into US buildings.
Last week, the sentencing phase of Moussaoui's trial began, in a federal court-house in Alexandria, Va.
There is only one thing at issue: whether Moussaoui will receive the death penalty or life in prison. But this phase could last weeks, or months, as prosecutors present a lengthy case that attempts to tie him directly to Sept. 11.
By not telling law enforcement officials about the coming attacks, Moussaoui might as well have piloted one of the hijacked jetliners himself, under prosecutors' theory of his case. He was already in jail on Sept. 11, having been arrested following suspicious actions at a flight school in Minnesota.
Some analysts find this a reasonable approach. Moussaoui took many of the same actions that the Sept. 11 hijackers did, and for a time was even thought to be the so-called "20th hijacker". He has said he met Osama bin Laden, and that he was supposed to fly an airplane into the White House at some point. Clearly, he knew something big was going on. Proving he was part of the actual operation is perhaps unnecessary.
"We'd have no problem holding Osama bin Laden guilty [for 9/11]," says Ronald Rotunda, a professor of law at George Mason University. "He was at the center of the conspiracy."
Some other experts aren't sure the prosecution strategy will work. Moussaoui pleaded guilty only to being part of an overall Al Qaeda army, not to participating in Sept. 11 in particular. If he had told prosecutors, would they have believed him? Could they then have stopped the operation?
"I think the government's case is really difficult," says Ms. Kayyem. "It's not clear that even all the hijackers really knew what they were participating in."
The judge in the death penalty trial has warned prosecutors that they risk putting their case on shaky ground if they take their argument too far.
"I don't know of any case where a failure to act is sufficient for the death penalty as a matter of law," said US District Judge Leonie Brinkema last Thursday, after the jury had left the courtroom.
Not that the US is the only nation struggling with a terrorism case. Take Spain, where Immad Yarkas, alleged leader of an Al Qaeda cell, last fall was convicted of helping with the underpinnings of the Sept. 11 conspiracy.
Now prosecutors think there may not be enough evidence to uphold that conviction, and the 15-year sentence that came along with it. Even if it is struck down, however, Yarkas will remain imprisoned. He received a separate 12-year sentence on a charge of belonging to a terrorist group.
To this point Yarkas is the only person convicted in civilian court of participation in Sept. 11.
But one thing the Moussaoui case has allowed the US government to do is to produce a version of the 9/11 trial that America has never had.
One of the first things prosecutors did last week, for instance, was read a minute-by-minute account of the hijacking of American Airlines Flight 11 and its flight into the World Trade Center north tower. The point was to establish some connections between the behavior of the hijackers and that of Moussaoui, but the side effect was to electrify the courtroom, as most present bent to hear the last words of flight attendant Amy Sweeney, "We are way too low!"
Subsequent testimony has dealt with Moussaoui's flight training, the suspicions of his instructors, and the details of his subsequent FBI interrogation.
Family members of Sept. 11 victims are watching the trial at remote viewing stations located in five federal courthouses around the country. They will be allowed to testify as to the harm done to them by the terror attacks if the trial jury determines Moussaoui is eligible for the death penalty.
So far, the Moussaoui trial has eaten up four and a half years, and produced numerous unpredictable moments. The judge has allowed the defendant to serve as his own lawyer, only to reverse herself months later; a defendant who seemed implacable at first subsequently pleaded guilty, though to what, exactly, remains to be determined.
Will the US ever attempt a similar prosecution?
"The lesson they're taking from this is 'never again,' " says Jeremy Shapiro, a foreign policy fellow at the Brookings Institution.