WASHINGTON, Sept. 24 - When the United States sent Maher Arar to Syria, where he was tortured for months, the deportation order stated unequivocally that Mr. Arar, a Canadian software engineer, was a member of Al Qaeda. But a few days earlier, Canadian investigators had told the F.B.I. that they had not been able to link him to the terrorist group.
That is one of the disclosures in the 1,200-page report released last week after a two-year Canadian investigation of Mr. Arar's case found him to be innocent of any terrorist ties. The report urges the Canadian government to formally protest the American treatment of Mr. Arar, a recommendation Canadian officials are considering.
Mr. Arar, 37, who now lives in British Columbia, has a lawsuit against United States officials and agencies that is on appeal, and he has demanded an explanation for his treatment from the Bush administration.
A close reading of the Arar Commission report offers a rare window on American actions in the case, describing seemingly flimsy evidence behind the American decision in 2002 to send Mr. Arar to a country notorious for torture; a deliberate attempt by American officials to deceive Canada about where Mr. Arar was; and lingering confusion among top American officials about the two countries' roles in the case.
President Bush earlier this month acknowledged for the first time that high-level people suspected of being terrorists had been held in secret prisons overseas by the Central Intelligence Agency. But he and other officials have said nothing publicly about the American practice of rendition, in which dozens of suspects have been seized and turned over for interrogation to other countries, including several known to engage routinely in torture.
Cases like that of Mr. Arar would not be affected by the compromise legislation on detainee treatment worked out between the White House and Republican senators last week, since it would have no effect on interrogation methods used by other countries. In fact, the proposed bill would strip non-Americans held overseas under United States control of the right to challenge their detention in federal court.
"It's a huge hole in what Congress is doing," said Michael Ratner, president of the Center for Constitutional Rights in New York, which represents Mr. Arar in his lawsuit. "The government can still send people secretly to other countries where they'll be tortured."
For nearly four years, the United States government has refused to make public any information on the case of Mr. Arar, which has become an international symbol of American excesses in the campaign against terrorism. The Bush administration refused to cooperate with the Canadian commission, so many questions about American actions and motives remain unanswered.
But Mr. Arar's case is more public than other cases of rendition, because he was detained inside the United States and legally deported, creating a modest paper trail. The three-volume report describes Canadian contacts with American officials in meticulous detail, offering by far the fullest account of any rendition case to date.
The commission's report says inexperienced Canadian police officials originally passed inaccurate information to the United States linking Mr. Arar to terrorism, based largely on his acquaintance with other men under suspicion.