The first Guantanamo detainee to face a civilian trial is a “mass murderer” who played a key role in the terrorist bombings of two U.S. embassies in Africa in 1998, a prosecutor said Monday in closing arguments.

Defense claims that Ahmed Ghailani was an unwitting dupe in the plot “flies in the face of the evidence and it flies in the face of common sense,” Assistant U.S. Attorney Harry Chertoff told jurors in federal court in Manhattan.