The first Guantánamo Bay, Cuba, detainee to face a civilian trial was acquitted Wednesday of all but one of the hundreds of charges that he helped unleash death and destruction on two U.S. embassies in 1998, a mixed result for what's been viewed as a terrorism test case.

The first former Guantánamo Bay, Cuba, detainee to be tried in federal criminal court was found guilty on a single conspiracy charge Wednesday but cleared on 284 other counts, an outcome that will seriously undermine the Obama administration’s plans to put other Guantánamo detainees on trial in U.S. civilian courts.

A jury of six men and six women in New York found Ahmed Ghailani, 36, guilty of conspiracy to damage or destroy U.S. property but acquitted him of multiple murder and attempted murder charges for his role in the 1998 bombings of U.S. embassies in East Africa.

The Obama administration had hoped a conviction on most, if not all, of the charges would help clear the way for federal prosecutions of other Guantánamo detainees, including Khalid Sheik Mohammed and four co-conspirators accused of organizing the Sept. 11, 2001, attacks. The administration did not want to rely exclusively on the military commissions the Bush administration had made a centerpiece of its detention policy.

President Obama’s strategy, however, has run into fierce, cross-party opposition in Congress and New York, in part because of concerns that it would be harder to win convictions in civilian court.

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The failure to convict Ghailani, a native of Tanzania, on the most serious terrorism charges will bolster the arguments of those who say the military prison at Guantánamo Bay should be kept open, to host military commissions for some prisoners and to hold others indefinitely and without trial under the laws of war.

U.S. District Judge Lewis Kaplan thanked the jury, saying the outcome showed justice “can be rendered calmly, deliberately and fairly by ordinary people, people who are not beholden to any government, even this one.”

Department of Justice spokesman Matthew Miller said U.S. officials “respect the jury’s verdict” and are “pleased” Ghailani faces a minimum of 20 years and a maximum of life in prison at sentencing Jan. 25.

Ghailani is the fifth person convicted for his role in the bombings in Nairobi, Kenya, and Dar es Saalam, Tanzania, that killed 224 people, including 12 Americans.

Ghailani, a former Islamic cleric, was captured in Pakistan in July 2004 and turned over to the CIA, which held him in secret prisons overseas before he and 13 other detainees were transferred to Cuba in September 2006.

Prosecutors had branded Ghailani a coldblooded terrorist. The defense portrayed him as a clueless errand boy.

On the eve of the trial last month, Kaplan barred the government from calling a key witness because the witness had been identified while Ghailani was being held at a secret CIA prison where harsh interrogation techniques were used.

Material from The Associated Press is included in this report.