ALEXANDRIA, Va., Apr 6: Former New York City Mayor Rudolph Giuliani described watching desperate people jump from the burning World Trade Center in emotional testimony today to a jury that will determine if September 11 conspirator Zacarias Moussaoui should die.

Jurors and spectators, including relatives of the September 11 victims, also watched video clips of two planes hitting the trade center and then about five minutes of footage of people jumping from the burning, smoking buildings. Many spectators gasped and dabbed at tears while watching the video.

''I saw several people, I can't remember how many, jumping,'' Giuliani said. ''There were two people right near each other. It appeared to me they were holding hands.

''Of the many memories, that's one that comes to me every day.'' Shortly after, jurors were shown several views of the Twin Towers collapsing in Manhattan on September 11.

Moussaoui alternated between smiles and nods as he watched the video clips of the twin towers collapsing in Manhattan.

After the jury and judge were gone for the morning break he sang out ''Burn in the USA!'' -- an apparent takeout on the Bruce Springsteen song.

Last year, Moussaoui, an admitted al Qaeda member and the only person charged in the United States with the September 11 attacks, pleaded guilty to six counts of conspiracy. Three of the charges carry the death penalty.

On Monday, the jury found Moussaoui was eligible for the death penalty. The jurors agreed with the government argument that Moussaoui's lies when he was arrested three weeks before the attacks led to the deaths of nearly 3,000 people.

'NUCLEAR CLOUD'

In this final phase of the sentencing trial, jurors will decide if Moussaoui should be sentenced to death or life in prison. Dozens of witnesses, including family members of people who died in the hijackings and people who were injured in the attacks, will testify in this phase about how they were affected by the hijackings.

Giuliani, who won high praise for his handling of the September 11 crisis, was the first major witness to do so. He described where he was that day, what he saw and what he felt.

''By the time the second plane hit, we knew for sure it was a terrorist attack,'' he said, sitting next to scale models of the World Trade Center.

''It was horrid,'' he said, describing the site of the Twin Towers after they collapsed. ''The worst thing I've ever seen in my whole life ... parts of human bodies ... hands or legs.'' Giuliani said said it looked like a ''nuclear cloud'' was going through Manhattan after the towers collapsed.

Calling September 11, 2001, ''the darkest day in American history,'' federal prosecutor Robert Spencer urged jurors to sentence Moussaoui to death for his part in the disaster.

''Now it's time for you to hear the voices,'' he said. ''You cannot understand the magnitude of the horror that day, unless you hear it from the families.'' But Gerald Zerkin, one of Moussaoui's court-appointed lawyers, urged jurors to keep an open mind and listen to evidence that the defendant had a mental illness that caused him to be involved in the conspiracy.

''The government's evidence will present an extraordinary challenge for you. You must somehow maintain equilibrium,'' he said. ''You must nevertheless open yourselves to the possibility of a sentence other than death.''

Reuters