The nine men and three women on the jury started their deliberations following a turbulent six-week trial, featuring the horror and heartbreak of the 2001 attacks.
They must decide whether Moussaoui, a 37-year-old Frenchman and the only man tried in the United States over the attacks, will die by lethal injection or spend the rest of his life in jail with no chance of release.
"There is no place on this good Earth for Zacarias Moussaoui," said prosecutor David Raskin, in an empassioned closing argument.
"There is only one penalty that fits this crime and this defendant, ladies and gentleman, and that is the death penalty."
Defence lawyer Gerald Zerkin, however, argued executing Moussaoui would be self-defeating for America.
"He wants you to sentence him to death, he is baiting you to do it. Death is what he wants and what he can only get if you accommodate him."
He urged jurors to condemn Moussaoui to the "long slow death of a common criminal," and not the glorious jihadist's demise he yearned for.
Moussaoui said he would have participated in the September 11 attacks if he had not been arrested the previous month on immigration charges.
The same jurors have already found Moussaoui eligible for the death penalty, accepting prosecutors claims his "lies" while in jail helped facilitate the carnage of September 11, 2001.
Any decision to sentence him to death must be unanimous. As he was led away to the cells, Moussaoui, his face creased in a cynical smile, raised his hands in the air and clapped loudly.
Earlier he had chanted, after seeing prosecutors show gruesome pictures of severed limbs littering the ground outside the World Trade Center in New York: "there is more than one way to skin the American pigs."