"He was not a soldier, he was a driver," Mohammed said in a four-page transcript of his written testimony.
Attorneys for Hamdan presented Mohammed's account as their final evidence at the first U.S. war crimes trial since World War II. A jury of six American military officers is scheduled to hear the judge's instructions and begin deliberations on Monday.
Hamdan, a Yemeni with a fourth-grade education, faces a maximum life sentence if convicted of conspiracy and supporting terrorism.
During the two-week presentation of trial evidence, Hamdan's interrogators testified that he carried a pistol to protect bin Laden, had advance knowledge of terrorist "operations," and swore an oath of loyalty to the al-Qaida chief.
But the terrorist military leader made clear he had too low an opinion of Hamdan and other "illiterate" drivers to include them in any secret planning.
"His nature was more primitive (Bedouin) person and far from civilization. He was not fit to plan or execute," said Mohammed, who described himself as "the executive director of 9/11" in the transcript that was translated from Arabic.
As a notorious enemy of the United States, Mohammed makes an unlikely defense witness. Prosecutors warned he might try to subvert the trial and attempted to block his testimony. But defense lawyers said his input is critical, likening him to the "godfather" figure in an organized crime trial.
Mohammed said he saw Hamdan more than 50 times, including the day of his November 2001 capture at a roadblock, when the driver was assigned to evacuate the wives and children of al-Qaida members from southern Afghanistan to safety in Pakistan following the U.S.-led invasion.
But he said the Yemeni only stayed with the al-Qaida chief for the US$200-a-month salary.
"He was not with the ideology of Osama bin Laden, and people like him, he was only searching for pleasure and money in this life," Mohammed said.
Hamdan, who is in his late 30s, is one of 21 prisoners facing charges in the Bush administration's tribunal system for prosecuting terrorism suspects at this U.S. Navy base in southeast Cuba.
Hamdan's lawyers sought live testimony from Mohammed, who is representing himself in his own war crimes tribunal. But the Pakistani sent word he would not appear in court.
"He is intending to invoke self-incrimination rights and not appear," said Harry Schneider, a civilian defense attorney for Hamdan.
Another detainee witness, Waleed bin Attash, also refused to testify in court but agreed, like Mohammed, to respond in writing to answers provided by Hamdan's attorneys. Bin Attash said he was close enough to bin Laden to know that Hamdan "was not involved in the implementation of any attack."
Both witnesses were transferred to Guantanamo from secret CIA custody in September 2006 and face capital charges for their roles in the Sept. 11 attacks.
