Here is a look at the military commission system that will be used to prosecute five Guantanamo Bay prisoners charged in the Sept. 11 attacks:
WHAT IT IS: A military commission is a form of military tribunal convened to try people accused of unlawful conduct associated with war. They were commonly used for the first time during the 19th century Mexican-American War and have been modified over time by Congress and U.S. Supreme Court precedents. President George W. Bush and Congress authorized a military commission to try prisoners accused of terrorism and war crimes and held as prisoners at the U.S. Navy base in Guantanamo Bay, Cuba. President Barack Obama and Congress convened a new military commission, with several reforms aimed at addressing concerns of human rights groups and others, in October 2009.
HOW IT WORKS: A military commission trial is similar to a court martial in that the jurors are military officers, as is the judge. Many of the principles are the same as in both a U.S. civilian or military court: Defendants are innocent until proven guilty; the prosecution has the burden of proof; guilt must be proved beyond a reasonable doubt. As in a court martial, a conviction requires agreement by 2/3 of the jurors instead of the unanimous agreement required for a jury in civilian court. A military jury must be unanimous to impose a death sentence.
WHO HAS BEEN CONVICTED SO FAR: The Guantanamo commissions under Presidents Bush and Obama have resulted in seven convictions, two at trial and five through plea bargains.
WHY HUMAN RIGHTS GROUPS DON'T LIKE IT: Obama and Congress adopted several reforms in October 2009, including a prohibition on statements obtained by torture or cruel, inhuman or degrading treatment. But critics say the reforms don't go far enough, that the prosecution can still use statements and evidence from witnesses tainted by harsh treatment. Opponents of the military commissions also say that rules governing secrecy and the use of some forms of hearsay evidence will allow the U.S. to avoid a full accounting of the treatment of prisoners such as Khalid Sheikh Mohammed at secret CIA detention sites.
WHAT COULD HAPPEN: Mohammed and his four co-defendants all face charges that include murder, conspiracy and terrorism and could get the death penalty if convicted. They are scheduled to be arraigned Saturday but are not expected to enter pleas and the trial itself is likely at least a year away.