A casual observer could be forgiven this past week for thinking that the so-called "war on terrorism" is nearing a successful conclusion.

As the United States commemorated the one year anniversary of the killing of Osama bin Laden, senior members of the Obama administration asserted that al Qaeda is in its death throes. Chased out of former havens in Afghanistan by coalition forces, harried by U.S. drones in Pakistan's tribal areas, and lacking strong leadership, or even a name that carries cachet enough to rally its forces, the organization that once inspired fear across the globe now appears to be fading into irrelevance.

Adding to the perception of al Qaeda's demise, on Saturday, in a vast, prefabricated courtroom at Guantanamo Bay, five men accused of plotting the September 11 attacks on the U.S. faced charges in a military commission. One of these men, Khalid Sheikh Mohammed, the alleged mastermind of the 9/11 attacks, is perhaps the most notorious al Qaeda member after bin Laden, and one that many Americans long to see brought to justice.

Mohammed is accused of orchestrating an attack that not only claimed the lives of nearly 3,000 people but also tested the very values that the U.S. was built upon -- tolerance, justice, and respect for the equal rights of every individual. More than ten years later, Mohammed's trial offers a chance to reaffirm the U.S. commitment to these values by meting out true justice in a court of law to someone clearly intent on destroying that commitment. But justice can't be found in a military commission at Guantanamo.

On Saturday, Mohammed and his co-defendants were arraigned on charges of conspiring in the 9/11 attacks. In due course, after pretrial motions, a trial will begin before a military judge and a verdict will be decided by a military jury. If convicted, all five face possible death sentences. But even if these men are truly guilty of the crimes charged, their trial will not be fair. Each will have the right to counsel, and be presumed innocent until proven guilty beyond a reasonable doubt, yet these important trappings of a fair trial belie the injustice lying beneath the surface.

In the military commissions at Guantanamo, multiple levels of hearsay may be admitted, denying a defendant any real right to confront witnesses against him; the prosecutors have a say in what witnesses the defense can call, and the court lacks any real independence -- a military official aligned with the prosecution hand-picks the judge and pool of jurors.

Perhaps most troubling, though, is that despite significant improvements to the military commission rules -- including a ban on the admission of evidence directly obtained by torture -- evidence indirectly obtained by torture, and coerced statements from witnesses, can still find its way into the trial. This is no theoretical risk: we already know each man on trial was held incommunicado by the CIA, forcibly disappeared, seriously abused, and denied access to a lawyer by agents of the U.S. government.

Some news reports have suggested that the abuse Mohammed suffered is one reason he won't plead guilty. In an administrative hearing in Guantanamo in 2007, Mohammed admitted his role in plotting the 9/11 attack and other crimes, such as the execution of Wall Street Journal reporter Daniel Pearl in February 2002. A guilty plea now would relieve the prosecution from having to turn over evidence of his torture; a not guilty plea, some claim, would be Mohammed's way of having the last word by making the trial not about his own crimes but about the inhumane treatment to which he was subjected.

This trial may indeed expose torture and cast the U.S. in an unflattering light. But if so, it will simply be exposing the truth, a truth that is otherwise swept under the rug given that the Obama administration has refused to investigate alleged crimes of torture committed during the Bush administration.

The U.S. cannot un-torture Mohammed. It cannot redo the detention of these men in a way that is humane and just. There is, however, the chance to ensure that the court in which they are judged for their heinous crimes is not a further perversion of the values Americans claim to hold dear.

By trying these men in a second-class justice system, the U.S. government is sending a message to terrorists around the world that the United States can be pushed by fear into sacrificing fundamental values. Terrorism may indeed have the last word.

Andrea Prasow is senior counterterrorism counsel and advocate at Human Rights Watch. She watched the arraignment via closed circuit television set up by the Office of Military Commission at Ft. Meade military base in Maryland.