They include an Australian citizen, two men from Yemen and one from Sudan.
The Australian -- David Hicks -- is accused of fighting for Al-Qaeda in Afghanistan. The others are alleged to have provided security for Osama bin Laden and helped the group that carried out the 11 September 2001 attacks in the United States.
Yesterday, a U.S. military spokeswoman, Navy Lieutenant Susan McGarvey, said the men will receive a fair trial.
"[The] military commissions will provide a full and fair trial for each defendant," McGarvey said. "The accused will be able to present witnesses, evidence, there's the presumption of innocence, as well as each charge needs to be proven beyond a reasonable doubt in order to reach a finding of guilty. So we believe that in the course of the next weeks and possibly months the world will determine that these are full and fair trials."
McGarvey explained what the U.S. government will have to prove in order to win a guilty verdict.
"For conspiracy [the prosecutors] need to prove that the individuals knew the organization that they were joining, that they intended to join that organization and that they knew the end goals of that organization, and in this case it would be to kill American military and civilians," McGarvey said. "So that is the basis of the charge."
The tribunals were authorized by U.S. President George W. Bush after the 2001 attacks. Bush argued the tribunals were necessary to protect U.S. security interests.
But international rights groups have criticized the tribunals for -- they say -- failing to meet minimum standards of justice. Among other things, they point out the tribunals will allow hearsay evidence. In addition, conversations between defendants and their attorneys -- in some instances -- can be recorded. The appeals process will be restricted.
Others say that given the composition of the tribunals -- with military officers serving as jurors -- it's unlikely that the men will receive a fair trial.
Sam Zia Zarifi of the New York-based rights group Human Rights Watch said: "Our concern is that the process is not really set up for justice, but rather to give the appearance of justice. And we're very anxious to see what the outcome will be. Our fear is that the outcome is more or less predetermined."
Zia Zarifi criticized the decision to hold the trials at a base in Cuba and not -- technically at least -- on the territory of the United States, where the defendants would enjoy legal protections provided by the U.S. constitution.
"The choice of Guantanamo as the physical location for these tribunals is itself indicative of our concerns," Zia Zarifi said. "There is no particular reason from the standpoint of national security why a courthouse for these particular detainees could not be arranged on American soil. The sole purpose really seems to have been to keep these detainees away from access to American justice, and that's very problematic."
The last time the United States made use of such specialized tribunals was in 1942 for the trial of suspected Nazis.
So far Bush has authorized hearings for 15 Guantanamo detainees. The fate of most of the other prisoners remains unclear.