Ghailani guilty of one charge for 1998 US embassy bombs
The first Guantanamo detainee tried in a US civilian court has been found guilty on just one out of 285 terror charges over the 1998 bombings of US embassies in East Africa.
Tanzanian Ahmed Ghailani, 36, was found guilty of conspiracy to damage or destroy US property with explosives.
But he was cleared of many other counts including murder and murder conspiracy.
Ghailani faces a minimum of 20 years in prison. The verdict comes as the US weighs other civilian terror trials.
The BBC's Iain Mackenzie, in Washington, says the verdict in the Ghailani case will be seen as a huge blow to the Obama administration.
It hopes to try other Guantanamo detainees in civilian courts - including alleged 9/11 mastermind Khalid Sheikh Mohammed.
Officials will now be considering how to proceed, but it could mean the controversial prison remains open for some time to come, our correspondent adds.
The attacks on US embassies in Tanzania and Kenya killed 224 people and were one of al-Qaeda's first international shows of strength.
Four accused co-conspirators were convicted over the bombings in 2001 and sentenced to life in prison.
According to the indictment, Ghailani helped buy the Nissan lorry, oxygen and acetylene tanks used to destroy the US embassy in Dar es Salaam, Tanzania, and helped load boxes of explosives into the back of the lorry ahead of the bombing.
US investigators said Ghailani flew to Pakistan the night before the simultaneous bombings.
He was charged in the US in March 2001 but remained at large in Afghanistan and the Waziristan area of Pakistan, the US says. He was captured in July 2004 and transferred to Guantanamo Bay in 2006.
Last year, the US stayed proceedings in a military tribunal at Guantanamo Bay and transferred him to New York for the civilian trial.
Defence lawyers, meanwhile, argued Ghailani was only an errand boy who had been duped by al-Qaeda operatives, framed by contaminated evidence and knew nothing of the bomb plot.
After the verdict was announced on Wednesday night and the jury left the courtroom, the former Guantanamo Bay prisoner rubbed his face, smiled and hugged his lawyers. He will be sentenced on 25 January.
US Justice Department spokesman Matthew Miller said in a statement: "We respect the jury's verdict and are pleased that Ahmed Ghailani now faces a minimum of 20 years in prison and a potential life sentence for his role in the embassy bombings."
During the trial, prosecutors suffered an early setback when federal Judge Lewis Kaplan in New York barred a key government witness from testifying, saying he had been named by Ghailani while the latter was "under duress".
Mr Ghailani was detained in Pakistan in 2004, taken to a secret CIA facility and then to Guantanamo Bay in 2006.
He was subject to what the government refers to as "enhanced interrogation" by the CIA. His lawyers say he was tortured.
Despite losing its key witness, the government was given broad latitude to refer to al-Qaeda and Osama bin Laden throughout the trial.
Defence lawyer Peter Quijano welcomed the acquittals. He said the one conviction would be appealed, adding: "We still truly believe he is innocent of all these charges."