Zacarias Gump?

Attorney Andrew Cohen analyzes legal issues for CBS News and CBSNews.com.

Moussaoui even played the part Monday here at his sentencing trial in Alexandria, Virginia, sitting quietly in the corner of the federal courtroom, like he was in a long and important time-out.

Was this plump man the linchpin to the biggest criminal investigation in the history of the world, as prosecutors claim? Was the slothful, slouching guy in the green jumpsuit the last best chance our nation's intelligence community had to foil the worst attack in American history? Can it be that he, of all people, is the hinge of the post-Sept. 11 history we have only just begun to write?

Government attorney Rob Spencer told jurors that had Moussaoui told the truth one month before the attack, when he was questioned by law enforcement officials in Minnesota, the feds surely would have unraveled the 9-11 plot in the 25 days between the day of Moussaoui's arrest on immigration charges and the day the Twin Towers fell.

Or, failing that, Spencer said, the government at least would have been able to better protect airplanes and their passengers. "It would all have been different," Spencer wistfully told the panel at the beginning of an unusual trial that seems destined to be all about what might have been.

If Moussaoui hadn't lied -- he told agents back then nothing of his connections to Al Qaeda or his plans to fly planes into buildings -- the government "would have" prevented the 9-11 deaths, Spencer told jurors.

The Federal Aviation Administration "would have" beefed up cockpit security, enhanced its do-not fly list, and prevented box cutters from being brought onto planes, and law enforcement officials "would have" undertaken an "all out press" to locate and then capture Moussaoui's confederates. From accurate information provided by Moussaoui, all four pilot hijackers from 9-11, and seven of their colleagues, "would have" been quickly traced, tracked, and presumably arrested, Spencer said.

The prosecution needs to make Moussaoui into this font of all knowledge to convince jurors that his actions directly resulted in at least one 9-11 death.

Even as they conceded today that he was not, as previously advertised, the "20th hijacker," they need to make the jury believe that all the authorities were missing in their pre-9-11 cache of information was some "inside" information from a guy with "credible" and "timely" information about a terror plot. That guy was Moussaoui, they claim, and had he talked, the enormous expanse of the government would have listened.

When you hear Spencer describe Moussaoui's role -- when he tells you what the feds would have done with the information Moussaoui should have given them -- it all makes sense in the way a football game makes sense the next day after you've watched the videotape, seen which players blew their coverage, and know how it all turns out.

Of course it seems easy now to trace back the steps and say that the plot would have been foiled with just a bit more information. Even from the government's perspective -- and to his credit, prosecutor Spencer made no attempt to hide it -- this is a Monday morning quarterback trial of woulddahs, coulddahs, and shoulddahs. The question is to which side jurors will offer the benefit of their reasonable doubts.

Spencer, knowing that the strongest part of the government's case is the crime itself, immediately upon getting to the podium brought jurors back to the morning of 9-11. In fact, his first words to the jury were: "September 11, 2001 dawned clear, crisp and blue… It started as an utterly normal day" that soon turned into "a day of abject horror" filled with "pain, misery and death."

Spencer then portrayed Moussaoui as a member "in the thick of" the 9-11 plot whose job "as a good, loyal al Qaeda soldier" was to lie to the police if arrested "to allow his brothers to go forward." His lies had their intended effect, Spencer said, which was to deflect investigators away from the true nature of Moussaoui's plans -- and the plans of the hijackers.

In order to buy into the government's theory, jurors are going to have to be willing to presume that the nation's law enforcement community, prior to 9-11, was up to the challenges we now know it wasn't. Jurors will have to give credit and faith to a bunch of federal agencies that surely before that awful day, and in many ways since, have not deserved much. They will, in many ways, have to allow themselves the luxury of, in the words of the defense, "dreaming" of things that might have been.

So will the panel forgive the government for its pre-9-11 sins in order to pay Moussaoui for his? That's the question now that this trial is finally underway.
By Andrew Cohen