(CBS) CBSNews.com Legal Analyst Andrew Cohen has been keeping track of the government's case against the so-called "20th hijacker" through all its twists and turns.

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What does Zacarias Moussaoui's terror conspiracy trial next month have to do with the only known audiotape recording of firefighters inside the Twin Towers of the World Trade Center?

Why in the world would New York City fire officials forbid firefighters and their families from publicly disclosing the contents of the tape when those contents so obviously are a poignant and vital part of American history?

The answer says a lot about how government attorneys intend to go after the man some say was training to be a Sept. 11 hijacker.

The party line from fire officials, reported in Sunday's New York Times, is that the substance of the tape shouldn't be disclosed now because it may be needed as evidence by prosecutors at Moussaoui's September trial. But surely prosecutors don't need the contents of the tape to prove that Moussaoui was a co-conspirator in the Sept. 11 attacks on America.

Indeed, nothing in the tape would or could prove or disprove Mousasoui's alleged role in the plot — unless, preposterously, the firefighters themselves were talking about Moussaoui as they went about their doomed rescues. Besides, the government has plenty of more direct and complete evidence than the tape that proves that the planes hit the towers and that the towers fell.

So, if the party line from fire officials is true, it means that government attorneys want to play the tape for jurors during the penalty phase of a Moussaoui trial — if the defendant is convicted of one or more of the capital charges against him.

Prosecutors no doubt want to use the tape to impress upon jurors in the most dramatic and genuine way possible the manner in which the massive attack affected the most heroic of individual victims. That means, in other words, that federal prosecutors intend to present a highly emotional courtroom case against Moussaoui in an effort to convince jurors that he deserves the death penalty despite the fact that he was sitting in jail on the morning of Sept. 11.

Can you think of anything more emotional in that otherwise sterile federal court setting in Alexandria, Va., than hearing the actual voices of actual firefighter victims just minutes or seconds before they perished? I bet there won't be a dry eye in the house. And any juror thinking that Moussaoui's relatively minor role in the crime offsets the enormity of the crime itself — any juror leaning toward life versus death as a penalty — will have a hard time maintaining that position after hearing the haunting voices of, literally, the bravest of the brave. If trial is theatre, the feds are setting up the jury for a real tearjerker.

There's nothing wrong with presenting a dramatic, sorrowful, cue-the-tears criminal case. Federal prosecutors did it with great success during the Oklahoma City bombing trial of Timothy McVeigh, who was convicted in June 1997 after a trial that brought virtually everyone in the courtoom (except McVeigh and U.S. District Judge Richard Matsch) to tears. McVeigh was sentenced to death and executed last June. His co-conspirator, Terry Nichols, was convicted of conspiracy and manslaugthter (but not terrorism or murder) after a much less emotional trial of his own. Nichols got a life sentence.

McVeigh was much more involved in the crime than was Nichols but the lack of emotion from prosecution witnesses at trial also helped Nichols' cause. Don't think the Justice Department has forgotten that little lesson from the two Oklahoma City bombing trials. Since Moussaoui arguably is situated more closely to Nichols than to McVeigh when it comes to active participation in a terror attack (Nichols was home with his family when McVeigh detonated the truck bomb on April 19, 1995), raw emotion likely will be a critical component of the government's case against the so-called "20th hijacker" who wasn't remotely close to an airplane when the terror attacks occurred.

Even with a group of Northern Virginia jurors who live and work in the shadow of the "other" target last Sept. 11 — the Pentagon — even with a group of people why aren't going to be very inclined to cut Moussaoui a break or even to comprehend his peculiar type of defense strategym prosecutors still will need drama and emotion to put Moussaoui on death row. So it's no wonder, really, why they want to hold the audiotape close to the vest until the trial. It's no wonder why they want it played publicly for the first time in a courtroom when virtually everything is at stake.

The tape is by most accounts poignant and heartbreaking, revelatory and heartening. It's also the government's trump card.