With 2 million men and 200,000 women behind bars in the United States, the problem appears small — there were 344 substantiated incidents of staff sexual misconduct and harassment reported by authorities last year. But experts believe incidents are underreported, and the bureau study notes that many allegations remain under investigation.

Critics say just one improper relationship between staff and an inmate erodes discipline, security and morale in institutions where there is little privacy, few secrets and a strong reluctance to "snitch."

The few offenders also tar the reputation of all officers, undermining their authority.

"I’m looking for somebody who’s a leader in one of these agencies to come out strong and say this is absolutely intolerable . . . and the si- lence is deafening," said Brenda V. Smith, a professor at American University’s Washington College of Law and a member of the National Prison Rape Elimination Commission.

"There has to be very concrete steps to get past the code of silence that exists in these facilities," she said. "And it’s a code of silence not only for inmates . . . it’s also for staff.

While there is an element of supposed romance noted in many of the cases, sexual relations of any kind between prison employees and inmates are considered nonconsensual by law because of the inherent power that staff have over prisoners. In Virginia it is a felony punishable by up to five years in prison.

According to the Virginia Department of Corrections, from 2002 through 2005, there were 49 substantiated, or proven, allegations of staff sexual misconduct toward inmates.

Thirty-nine allegations were against female staff, and 10 were against male staff. As a result, 33 staff members have been fired or allowed to resign. At least one was prosecuted.

The number of substantiated sexual allegations against staff reported by the department was down sharply in 2005 — just four, compared with 16 in each of the two prior years.

"We can’t explain why there is a change or aberration," Corrections Department spokesman Larry Traylor said in an e-mail. "We will need 2006 and possibly 2007 data to further understand what this may mean."

Allen J. Beck, chief of corrections statistics at the U.S. Bureau of Justice Statistics, said that in 2005, about half of all substantiated incidents in prisons and jails, from forcible rape to sexual harassment, involved staff.

Nationally, about two-thirds of the offending prison staff — not jail staff — were women. In Virginia, three out of four substantiated offenses were by female prison staff.

"There are relationships that emerge, and sometimes they become inappropriate," Beck said. "It’s one of the challenges of working in those facilities. There’s vulnerability for both inmates and the staff."

His study found that 82 percent of prison or jail staff members involved in such incidents were fired or resigned, and 45 percent were arrested or prosecuted.

The extent of sexual abuse in prisons and jails is not known, Beck said. "Our job is to find that out. At this point, what we have is exactly what correctional authorities know and report to us. . . . We know that not all victims come forward."

Smith, among others, contends that sexual misconduct in prisons is less likely to be reported than in the outside community and, once reported, handled properly.

Those who agree note that if prisoners are reluctant participants, then they have a lot to lose because of their relative powerlessness and the likelihood that the staff members will be believed and the prisoners will not.

According to Beck, an estimated one-third of correctional staff in U.S. prisons and jails are females. Many of them work in male prisons.

Smith said it is not surprising that a larger number of female staff in prisons are involved in sex offenses. Male inmates outnumber female inmates more than 10-to-1. The federal report did not break down the data for homosexual versus heterosexual misconduct, but assuming most staff and most inmates are heterosexual, you would expect to find more female staff reported as perpetrators and more male inmates as victims, she said.

"You will often find that the culture that allows this kind of stuff to happen is also a culture that is particularly inhospitable to female staff," she said, noting that female staff might align themselves with inmates for protection.

In 1998 and 1999, a 17-year-old male held at Beaumont Juvenile Correctional Center in Powhatan County was investigated by state police for sex offenses with female staff there. In exchange for sex with female staff, he kept order among the younger inmates, he told The Times-Dispatch.

At least three female employees resigned or were asked to resign after an investigation. According to state police, authorities declined to prosecute anyone without physical evidence or independent witnesses.

Many problems occur because male officers in the United States work in female prisons and jails, contrary to international norms.

The U.N.’s Standard Minimum Rules for the Treatment of Prisoners say "no male member of staff shall enter the part of the institution set aside for women," said Jenni Gainsborough of Penal Reform International’s Washington office.

In June, two men died in a prison gun battle in Florida when an attempt was made to arrest six male officers who were accused of having sex with female prisoners.

And last month, former Lt. Bobby G. Brown Jr., who supervised female inmates at Pocahontas Correctional Center in Chesterfield County, was sentenced to six months after fathering the child of inmate Sheron M. Montrey.

Last year, three former Pocahontas inmates, including Montrey, told The Times-Dispatch that they had sexual relations with male employees, and that such relationships were common and known to officials there.

A fourth former inmate said she was transferred from Pocahontas for complaining she was sexually harassed by a supervisory officer. Male staff accused of such relations apparently were not punished or allowed to resign, the inmates alleged.

A corrections officer, who asked the newspaper for anonymity, said last year that "once there’s even the slightest bit of impropriety" with an inmate, "they own you."

Smith, of the National Prison Rape Elimination Commission, was critical that jail and prison authorities reporting the incidents were allowed to characterize relationships as romantic in the study and did so for 68 percent of the substantiated cases of sexual misconduct or harassment involving staff.

Meda Chesney-Lind, a criminologist and professor of women’s studies at the University of Hawaii, said she was amazed by the bureau’s figures on female staff offenders.

"I have a hard time believing that such a large part of this violence is female . . . but this is definitely something to look at," she said. She also believes the word romantic is not appropriate. "It’s about power and abuse. It’s not about romance."

Smith said that when such relationships, even supposedly romantic ones, go bad, inmates can be transferred, put in segregation, lose "good-time" sentence reductions or have a bad mark on their record when they are up for parole.

Smith and many others, including Virginia officials, do not believe the answer to the problem is prisons with same-sex staff.

Corrections Department spokesman Traylor said that before the 1964 Civil Rights Act, Virginia had exclusively male staff at male prisons and female staff at its sole female prison.

The Civil Rights Act and subsequent regulations prevent discrimination against a person in employment based on gender, Traylor said. There is an exception in limited situations where a prisoner’s privacy rights are at risk, he said in an e-mail.

The department must maintain a balance between being an equal-opportunity employer and ensuring that the legitimate privacy rights of prisoners are respected, Traylor said.

"The issue is not male officers and female inmates or female officers and male inmates," he said. "Rather it is an issue of proper boundaries between staff and inmates whether they are of the opposite sex or of the same sex."

Just one relationship between a staff member and an inmate can be corrosive, Chesney-Lind said. "It’s a kind of toxic situation. It’s a kind of corrupt situation, and everybody knows about it."

Smith agreed with Traylor that there should be some gender-specific posts in men and women’s prisons.

Traylor said, "In general the privacy rights of offenders are limited to not being touched in certain places by a member of the opposite sex and not having certain parts of their bodies viewed by members of the opposite sex in the normal course of operations."

Smith said prisons staffed with officers of the same sex might seem desirable, but few courts would be willing to impose it. The answer, like the problem, is a lot more complicated, she believes.

Staff-on-inmate offenses could be curbed if prison leadership took strong steps to break the code of silence in prison and give staff and inmates better training about what is and is not appropriate behavior.

Smith said there also must be strong punishments imposed on offenders. She said prosecutors often do not believe the cases are worth pursuing. If victims or witnesses see perpetrators are not punished, they will not come forward and report wrongdoing.