When American University official William (Bull) Evans-Smith went on trial on a murder charge in Leesburg during the summer, some jurors had an overriding worry: Would they be locked up during the trial?

"We talked about that from day one," said Christine E. Nelson, a juror in the trial that stretched over three weeks and generated daily headlines.

"I wondered when they were going to sequester us and how I would get my things," said Nelson, who envisioned the difficulty her husband would have trying to pick out her shoes and makeup each day.

But Nelson and her fellow jurors were surprised when they were sent home every night. Prosecutors, defense attorneys and judges say jurors should not have been fearful of being sequestered. The practice is rare, and the presumption that it happens all the time is a major reason many people fear serving on juries.

"It rarely happens with local cases anywhere in the nation," said U.S. Attorney Joseph E. diGenova of the District. The practice, he noted, is used more often in the federal courts than in state courts.

Although some states require juries to be sequestered during their deliberations, most juries make up their minds so quickly that the forced seclusion rarely lasts more than the time it takes to eat one meal.

Even in the federal courts it is unusual for a jury to be sequestered during an entire trial. "I would guess that it happens in the federal courts two or three times a year," said William R. Burchill Jr., general counsel to the administrative office of the U.S. courts.

In most states, sequestration, which is supposed to insulate a jury from publicity or hearing inadmissible evidence about a case, is up to the trial judge. Defense lawyers and prosecutors are free to request it, but most say they are fearful of what the jurors might think.

"You have to wonder about the impact on the jurors," said Fauquier County Commonwealth's Attorney Charles B. Foley. "Are they going to be mad as hell that the commonwealth's got them locked up in a room?"

"From a defense standpoint," agreed David H. Moyes, one of the attorneys who defended Evans-Smith and did not seek to sequester the jury, "you start locking the jury up and it makes 'em mad."

"It's serious business when you sequester a jury," said diGenova. And it is "a very expensive proposition," he said. The federal courts alone last year spent about $782,000 on sequestration expenses, Burchill said, a figure that does not include the $30 per diem fee paid to federal jurors.

Jurors who are forced to leave their homes must be provided with not only food, lodging and transportation but also a host of other services. Court aides must tend to details such as regulating the number of alcoholic beverages the jurors drink, censoring their reading material, screening live TV programs such as "The Tonight Show," learning the names of family doctors, separating smokers and nonsmokers, and scheduling religious services.

"We've done more sequestration in this district than in most," said Jim Davey, clerk of the U.S. District Court for the District of Columbia. Most judges, he said, believe that it is bad to keep jurors locked up and away from their families.

Montgomery County Circuit Court Judge John J. Mitchell said the last time he sequestered a jury was five years ago in a homicide case, and that was only during deliberations. There is no reason to lock up a jury "if you instruct jurors hard enough," he said.

"I guess I've done it four times in 12 years," said D.C. Superior Court Judge Fred B. Ugast, who cites the expense and inconvenience of sequestering. "The test is not whether they've heard about the trial . . . but whether they'll be fair," he said.

Another reason sequestration is rare in Virginia, Foley said, is that criminal trials in the state are historically short. "In Virginia, if you get a case that runs over one week, that's amazing."

Arlington prosecutor Henry Hudson said he believes that sequestering a jury can "excite their appetite" for more information and make the jurors think "there must be something out there that they don't want me to know."

But V. Britt Richardson Jr., deputy commonwealth's attorney in Fairfax County, said instances of jury misconduct are extremely rare, and he credits that to careful instructions from judges not to talk about the case with anyone, read the newspaper or listen to the news.

"They've jurors always indicated that they take their oath very seriously," he said. "We show confidence in jurors by not further inconveniencing them."

During the Leesburg trial of Evans-Smith, 65, who was found guilty of second-degree murder, Loudoun County Circuit Court Judge Carleton Penn admonished the jurors not to talk to anyone about the trial or listen to the news. They were escorted to lunch by sheriff's deputies and allowed to go home each day about 5 p.m.

After the trial, Nelson, one of the jurors, submitted an affidavit in which she claimed that a juror consulted an almanac at home during the week of deliberations.

Nelson said the information gleaned from the almanac about what time the sun would have been up the morning Barbara Evans-Smith, 64, was strangled with a pair of pantyhose was a critical finding for the jury and in part caused her to "unwillingly surrender" to a unanimous vote of guilty.

Evans-Smith's defense attorneys, Blair D. Howard and Moyes, have demanded a new trial because they say the information from the almanac and other statements allegedly made in the jury room were matters that were not heard in open court. Penn is to set a hearing date for the issues tomorrow.

"Theoretically, had they been sequestered, that individual would have never had access to the almanac and we wouldn't have had that problem," said Howard, who said he has never asked a judge to sequester a jury.

Howard said that if Evans-Smith is granted a new trial he will probably not request sequestration. Instead, he said, he would ask the judge specifically to admonish the jury that it is not allowed to go outside the evidence presented in court.

"I don't see any movement suggesting that it sequestration should be done more often," said Tom Munsterman, director of the Center for Jury Studies, part of the National Center for State Courts in Williamsburg. "It's something that everyone seems to want to avoid," he said.

Munsterman, who helped draft the American Bar Association's 1983 guidelines on sequestration, says there was a lot of discussion on whether the ABA should discourage sequestration but that his group stopped short of that stance. The guidelines, Standard 19, say a jury should be sequestered only for the purpose of insulating its members from improper information or influences.