On the afternoon of Feb. 9, Dexter Penick was arrested at his home in Alexandria and charged with abducting his former girlfriend. Alone in a holding cell that night, Penick ripped his shirt to shreds, tied one end to his bedpost and the other to his neck. By 4 a.m., he was dead.

"If we had any idea there was a problem he would have been on a suicide watch," said Michael E. Norris, Alexandria's sheriff. "He seemed fine when he came in. You just can't have a psychiatrist examine every single person who walks into a jail."

But Norris -- and officials at every level of the criminal justice system -- readily agree that there has been an alarming rise in suicides in local jails throughout the United States.

Although no official statistics exist, experts say that the number may have jumped to as many as 1,000 last year, compared with about 400 in 1979. Thousands of attempts were stopped in progress.

"The figures are a national disgrace," said Dick Ford, director of jail operations for the National Sheriffs Association.

"It's getting to be out of control," said Lindsay M. Hayes, author of the only national study of jail suicides. "There are certainly several hundred more committed now. The federal government is trying to help map out a prevention strategy, but the magnitude of the problem is enormous."

The national study, conducted in 1981 by the National Center on Institutions and Alternatives, counted 419 suicides in the nation's 17,000 jails during 1979, a rate 16 times greater than the overall national suicide rate.

In the general population, the suicide rate is less than 2 per 100,000 people, according to Justice Department statistics.

Locally, in addition to Penick's death, suicides have been reported in jail or police lockups in Montgomery, Fairfax and Prince George's counties and the District during the past year.

And officials say there were probably hundreds of suicide attempts, such as that of Brhan Alawte, who was being held in Arlington in November when he tried to hang himself. The man, who a court-appointed psychiatrist had said was a "very serious suicidal risk," has been in a coma since and is not expected to recover.

Last month, the Washington area Council of Governments set up a task force on corrections to focus on reducing the number of suicide attempts in local jails.

Authorites blame the increase in jail suicides on tough new drunk driving laws that impose jail penalties on even first-time offenders, crowded conditions in jails, and staff shortages in many areas of the country.

"You get a 24-year-old kid who's never been in trouble before -- a college boy who drank too much at the game maybe -- and he kills somebody on the Beltway going home," said Keith McKeown, assistant director of the National Coalition for Jail Reform. "When he starts sobering up, the first thing he's going to think about is how he has just ruined his life. Nobody knows what he might do."

The first week after Ohio began imposing mandatory 72-hour jail sentences on drunk driving offenders in March 1983, three persons arrested on drunk driving charges committed suicide in their jail cells. A fourth inmate, out on bond, went home to get a change of clothes and shot himself, Hayes said.

"Even the threat of jail for the first-time offender is enough to put some people over the edge," Hayes added.

Authorities said the national trend away from placing people with psychiatric problems into mental health facilities has contributed to the rise in suicides in jail. The National Institute of Corrections estimates that as much as 75 percent of America's jail population may be made up of people with mental disabilities.

Penick exhibited behavior that many medical experts say is common among potential jail suicides. He had been arrested twice earlier for assaulting his girlfriend, and police said he may have been severely humiliated by her rejection of him. He showed no sign of depression or instability during a routine screening, according to Alexandria police.

As was the case with Penick, more than half of all suicides in jails take place within 24 hours of incarceration. Three-quarters of the prisoners who took their lives were charged with nonviolent crimes, two-thirds were in isolation and more than a third were intoxicated.

Many people who study jail suicide say that the lack of statistical evidence is a major impediment to alleviating the problem.

Eight million people pass through American jails during the course of each year, according to the Bureau of Justice Statistics, but records of jail suicides -- if they are kept at all -- are sporadic and inconsistent.

For example, many jurisdictions do not count among jail suicides a person who hangs himself in a police lockup or who dies after being taken to a hospital.

"No sheriff or jail administrator in the country wants to talk about this," said Sheriff James A. Gondles Jr. of Arlington, where three men have killed themselves in the past five years. "No one wants to admit it happens in his jail."

"We are averaging 13 attempts a month in our jail," said Fairfax Sheriff M. Wayne Huggins. "We had 130 attempts last year alone."

He said that anyone being held in a Fairfax jail who shows signs of suicidal behavior is placed under constant observation, a procedure that Alexandria and Arlington officials said is followed in their jails.

Some law enforcement officials said that placing prisoners under such observation requires staff and facilities they do not have. "We need more staff and better training," said the sheriffs association's Ford. "We are only now starting to gather statistics and examine the problem."

Most U.S. jails hold fewer than 10 prisoners and have very small staffs, a fact that magnifies training problems, officials say. In addition, sheriffs often are elected officials with no specific corrections training or background. But many medical experts contend that suicides committed in jail are the easiest to prevent. They said most jailers lack proper psychological training and do not screen prisoners adequately during the crucial hours immediately after a person is arrested and booked.

"The existing policy in most police departments is that unless you see a prisoner actually try to hurt himself you should do nothing," said Dr. Bruce Danto, a former police officer and a member of a recently formed Justice Department Task Force on suicide prevention in jails.

"Police have been taught to look at people as either good guys or bad guys. Sometimes the situation is a lot more complex than that."

Many police and sheriffs are reacting to the problem by increasing the training required of their employes. The American Medical Association now issues guidelines for screening procedures that it says will drastically reduce the number of suicides.

Some jurisdictions have been spurred by lawsuits to transform the way they routinely handle their prisoners.

Last month, as a result of a suit brought by the estate of Vincent Garcia, a man who committed suicide while in jail in El Paso County, Colo., a U.S. District Court judge there ordered a new set of standards for screening inmates admitted to the local jail.

Like most jail suicides, Garcia was in isolation, he was arrested for drunk driving and he was intoxicated when he died, according to an autopsy. He had a history of arrests for drunk driving, but this was not known when he was incarcerated because no screening was conducted.

In addition to a $10,000 payment to Garcia's estate, El Paso must provide a series of safeguards, including:

* Intensive supervision of all inmates during the first 24 hours of their incarceration.

* Modification of the existing physical plant.

* Creation of a special ward for mental health observation.

* Implementation of intensive suicide prevention training for all jailers.

Isolation in cells appears to be at least partly responsible for the increase in jail suicides. Ironically, law enforcement officials point out, the use of isolation cells has increased because of the prison rights activism of the past decade.

"Isolation is the single greatest enhancement to suicide," said Joseph R. Rowan, executive director of Juvenile and Criminal Justice International and a former director of an AMA project to accredit jails for suicide-prevention techniques.

"People who really want to harm themselves won't do it in public. Isolation is the spark any depressed person needs to kill himself."

But law enforcement officials say that isolation was mandated by law.

"We've all been sued on double cells," said Alexandria's Norris. "Federal district court rulings forced us to cut out double bunks in 1977. That's been the trend across the country. So how do you go back?"