The jury has ended its fourth day of deliberations in the trial of four men accused of conspiring to bomb two U.S. embassies in Africa without a verdict.

Long before the embassy bombings trial began, U.S. marshals practiced for trouble — a defendant rushing toward the witness box in one scenario, an angry spectator leaping over the gallery rail in another.

With deliberations under way, the security team is looking ahead.

"The next tense moment will be when the verdict is announced," said Betty Ann Pascarella, one of several dozen members of the U.S. Marshals Service providing trial security. "I've never worked on something as intense as this."

The four men on trial are accused in the nearly simultaneous bombings at U.S. embassies in Kenya and Tanzania in 1998 that killed 224 people, including 12 Americans. Prosecutors say the men acted on orders from exiled Saudi millionaire Osama bin Laden.

Security for the city's fifth major terrorism trial in a decade was outlined in a 100-page plan.

At the federal courthouse in lower Manhattan, concrete barriers block the street and wire strung atop the adjacent jail is intended to prevent helicopter landings.

Inside, trial spectators must pass through two sets of metal detectors. There are security dogs and the building's wiring is checked for sabotage. The courtroom and surrounding hallways are monitored around the clock, including by video cameras.

"We're prepared for the worst," said U.S. Marshal Russell Qualliotine, one of those overseeing security. "This trial is being watched by the world."

That is not in doubt: Last week, in an annoucement related to the trial, the State Department warned Americans abroad that they may be the target of a recent threat from extremist groups linked to bin Laden.

The trial has been calm. The defendants are handcuffed and searched each day before being led through a windowless, third-floor bridge from the Metropolitan Correctional Center to the courthouse.

The defendants are held in two cells behind Courtroom 318, two men per cell. When court is called into session, the massive metal door is opened by a guard in a control booth.

The defendants are escorted into the courtroom one by one. Their feet are shackled throughout the proceedings, the chains shielded from the jury by a curtain.

"These guys have been quiet, not like the World Trade Center bombers," said Chief Deputy Frank Devlin, referring to the 1993-94 trial in which four men were convicted. "They were boisterous."

That wasn't always the case. Before the trial began, one of the defendants dashed across the courtroom during a preliminary hearing, getting within feet of a wide-eyed Judge Leonard B. Sand. Another defendant awaiting trial allegedly stabbed a jail guard in the eye.

In an emergency, the marshals all have assignments: Some would rush to protect the judge; others to guard the jury; still others to the defendants.

A special operations team based in Louisiana is on alert during the trial and can be summoned to New York within hours. There is an armory inside the courthouse.

The U.S. Marshals Service is the oldest law enforcement agency in the country, begun in 1789 when George Washington appointed the first 13 U.S. marshals. The service caught fugitives in 17,000 felony cases last year.

But its main mission is protecting the federal judicial system — judges, jurors, witnesses and defendants.

"We protect the courthouse; it's America's symbol of justice," said Joseph Guccione, senior inspector for the Judiciary Security Division in New York.