The panel of six jurors was reviewing evidence from a two-week trial at the Guantanamo Bay Navy base that has become the first full test of the Bush administration's system for prosecuting alleged terrorists.
Salim Hamdan, a Yemeni held here since May 2002, faces a maximum life sentence if convicted of conspiracy and supporting terrorism.
In closing arguments, prosecutors said Hamdan's service to the al Qaeda chief over five years in Afghanistan helped him execute terrorist plots including the Sept. 11, 2001, attacks on New York and Washington.
"He is an al Qaeda warrior," said Justice Department prosecutor John Murphy, pointing to the detainee sitting at the defense table in a white robe and tan sports coat.
Defense lawyers counter that Hamdan was merely a member of bin Laden's motor pool. His Pentagon-appointed attorney, Navy Lt. Cmdr. Brian Mizer, said in closing arguments that his client never joined al Qaeda and had no part in planning attacks.
"If every garage mechanic and driver knew the details and was involved in the planning of the attack, it never would have happened," Mizer said.
The judge, Navy Capt. Keith Allred, told jurors that four of them - a two-thirds majority - must find Hamdan guilty "beyond a reasonable doubt" to convict him.
Even if they find him innocent, Hamdan may not be released. The military retains the right to hold "enemy combatants" considered a threat to the United States - even those cleared of charges by the tribunals.
Most of the evidence against Hamdan came from U.S. federal and military agents who interrogated him in Afghanistan and Guantanamo, including one who said that Hamdan swore an oath of allegiance to the terrorist leader and expressed "uncontrollable enthusiasm" for his cause.
Allred urged jurors to evaluate that evidence in light of a U.S. policy that prevented interrogators from advising Hamdan of a right against giving incriminating statements.
"You must decide the weight and significance, if any, such statements deserve," Allred told the jurors, who were hand-picked by the Pentagon and flown to the base in southern Cuba for the case.
Hamdan was captured at a roadblock in southern Afghanistan in November 2001 with two surface-to-air missiles in the car. Prosecutors accused Hamdan of transporting weapons for al Qaeda and evacuating bin Laden to safety after learning he was about to launch terrorist "operations," including the Sept. 11 attacks.
The military has charged 21 of the roughly 265 men held at this U.S. Navy base in southeast Cuba on suspicion of terrorism or links to al Qaeda or the Taliban. Military prosecutors say they plan trials for about 80 inmates.
"Although Hamdan's trial will be seen as a landmark case in the tribunals, because it is the first in six years," said CBS News foreign affairs analyst Pamela Falk, "the next trial, that of Khalid Sheikh Mohammad - called the mastermind of the Sept. 11 attacks - will be the real bellwether, because it is a case that will raise the issue of harsh interrogations and because it is a death penalty case."
Falk, who traveled recently to Guantanamo, added that the jurors in Hamdan's case were expected to return a verdict fairly quickly, as it required a concensus of only four members.
So far, only one Guantanamo inmate has been convicted. Australian David Hicks reached a plea agreement that sent him home to serve a nine-month prison sentence.