Usama bin Laden's former driver offered the terrorist leader aid and protection that helped make the Sept. 11 attacks possible, prosecutors said Monday in closing arguments at the first Guantanamo war crimes trial.

Prosecutor John Murphy said evidence in Salim Hamdan's two-week trial showed the Yemeni detainee played a "vital role" in the conspiracy behind the 2001 attacks.

"There's an intricate pattern in which this accused helped in the preparation of and transportation of the leadership that made this possible," said Murphy, a civilian attorney with the Justice Department.

But Hamdan's Pentagon-appointed attorney countered that the defendant was merely a low-level bin Laden employee who never joined the Al Qaeda conspiracy against the United States.

"Not one witness said he had any role in the terrorist attacks themselves," Navy Lt. Cmdr. Brian Mizer said in closing arguments. "Mr. Hamdan is not an Al Qaeda warrior."

A jury of military officers is expected to begin deliberating a verdict later Monday in the case against Hamdan, who is charged with conspiracy and supporting terrorism. He faces a maximum life sentence if convicted at the first U.S. war crimes trial since World War II.

The judge, Navy Capt. Keith Allred, told the jury of six military officers that at least four must find Hamdan guilty "beyond a reasonable doubt" to convict him.

Allred reminded jurors that he allowed evidence from FBI interrogators who did not advise Hamdan of his right against self-incrimination and urged them to decide its merit for themselves.

"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.

Hamdan is one of roughly 80 prisoners that the Pentagon plans to prosecute in the tribunal system.

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.