The first Guantanamo detainee to face a civilian trial is a cold-blooded killer and terrorist who slipped away the day before his cohorts carried out a plot to attack two U.S. embassies in Africa in 1998, a prosecutor said Monday in closing arguments.

Ahmed Ghailani joined two known al-Qaida operatives on a plane to Pakistan, where they could "congratulate themselves on the massacre of innocents they have caused," Assistant U.S. Attorney Harry Chernoff told jurors in federal court in Manhattan.

Chernoff asked the jury to reject defense claims that Ghailani was an unwitting dupe for a terror cell. He said the men were thugs operating on orders from Osama bin Laden.

"This is Ahmed Ghailani. This is al-Qaida. This is a terrorist. This is a killer," he said at the close of a daylong argument. "I'm asking you to return a verdict of guilty on all counts."

Prosecutors allege Ghailani helped an al-Qaida cell buy a truck and components for explosives used in a suicide bombing in his native Tanzania on Aug. 7, 1998. The attack in Dar es Salaam and a nearly simultaneous bombing in Nairobi, Kenya, killed 224 people, including 12 Americans.

Authorities say that while Ghailani was on the run, he spent time in Afghanistan as a cook and bodyguard for bin Laden and later as a document forger for al-Qaida in Pakistan.

He was captured in 2004 and held by the CIA at a secret overseas camp before being transferred to Guantanamo in 2006.

After the decision to put the 36-year-old detainee on trial in New York, a judge dealt the government a setback by barring testimony from a key witness identified by the CIA. Harsh interrogations techniques used by the CIA made the evidence unconstitutional, the judge ruled.

Despite the decision, the government has been given broad latitude to reference al-Qaida and bin Laden.

The jury heard a former al-Qaida member who has cooperated with the government describe how bin Laden took the group in a more radical direction with a 1998 fatwa against Americans.

Bin Laden accused the United States of killing innocent women and children in the Middle East and decided "we should do the same," L'Houssaine Kherchtou said on the witness stand.

A prosecutor read aloud the fatwa, which called on Muslims to rise up and "kill the Americans and plunder their money wherever and whenever they can find it."

Other witnesses described how Ghailani bought gas tanks used in the truck bomb with cash supplied by the terror group, how the FBI found a blasting cap stashed in his room at a cell hideout and how he lied to family members about his escape, telling them he was going to Yemen to start a new life. Instead, prosecutors say, he boarded the one-way flight to Pakistan using a false name.

Ghailani's attorney was expected to give his closing argument on Tuesday followed by a government rebuttal.