Ten days after his wife was murdered with a butcher knife by a guest at his house, Jay Barber went for a walk with his two little girls, a walk he says haunts him as much as the murder itself.

Tiffany, then 3 years old, asked her father, "When is mommy coming home?" Barber remembers that he answered, "Your mother is dead and not coming home any more."

Barber's oldest daughter Kimberly, now 9 year old, saw part of the murder. She keeps asking to see the murderer so she can ask him why he did it.

The murderer, now 22, a former star athlete in high school who grew up in a middle-class family and who had never committed a crime until he stabbed to death a woman he hardly knew, said last week he couldn't answer Kimberly's question.

"I dont know. I just don't know," David J. Voetsch (pronoucned Voach) said in an interview at the Fairfax County jail during which tears welled in his eyes. "I'm sorry. But that'a nothing. There is nothing that can make it any better."

Voetsch's parents, who live near Mount Vernon, N.Y., and who heard about the murder by telephone one Sunday after they got home from church, say they still wonder what could have led their son to kill. "I lay in bed at 3 a.m.," said Arthur Voetsch, an engineer with New York Telephone, and I can't picture my kid doing that."

Rebecca Barber, a 29-year-old Fairfax County mother and wife, was murdered in her home three-and-a-half years ago. The crime, in its aftermath, uprooted her family and fills her relatives with hatred. It sent to jail an 18-year-old youth who says he is humiliated by his act and it plagues his parents with guilt. "It's the worst thing that has ever happened in this generation," said Colleen Smith, an aunt of the murdered woman.

This, then, is a story about how one bloody Saturday night in January 1975 haunts two American families, families sharing revulsion over the murder and a consuming interest in the man who committed it. It is a tale of vengeance and love, not unlike the aftermath of any of the 20,510 murders recorded in the U.S. that year.

The Jan. 26, 1975, murder, according to the Fairfax County prosecutor, was extraordinarily gory. "I have looked at a lot of murder scenes and dead bodies," Commonwealth's Attorney Robert F. Horan said, "but I've seen few, if any, to match this for pure viciousness."

The 20-minute attack, which ended with Rebecca Barber's death, began after a birthday party she and her husband gave a nephew, a soldier assigned to a military school at Fort Belvoir. Voetsch, a fellow soldier, was invited to the party with the nephew.

According to later testimony, Voetsch drank 14 cans of beer that night. It was decided he would spend the night at the Barbers' house in the Springfield area.

Around midnight Rebecca Barber was cleaning up the house, wearing only a bathrobe over her underwear, Voetsch made sexual advances toward Mrs. Barber and was rebuffed, prosecutor Horan said at the trial.

Voetsch himself refuses to discuss the chronology of the murder, and no one except Voetsch and his victim saw what happened in the beginning.

A wakened by his wife's screams, Jay Barber attempted to defend her. But Voetsch, a man of immense physical strength who, lying on his back, can lift 320 pounds above his chest, stopped him with one punch that crushed the left side of Barber's face and knocked him unconscious. His wife, according to Horan, died when Voetsch stabbed her back with a butcher knife as she was trying to phone for help. The force of the blow broke the knife's blade.

Sometime during the attack, 5-year-old Kimberly awoke, went to her parents' bedroom and looked in. She has told her father that she saw two people struggling on the floor, and that Voetsch told her, in an angry voice, to go back to bed. Horan said that from his investigation of the murder he thinks Kimberly saw the knife blow that killed her mother.

Since the murder, the victim's family has split apart. Jay Barber spent 10 days in Fairfax Hospital recovering from the blow that permanently damaged the vision of his left eye. After paying more than $2,000 to replace the carpeting ruined by blood and to clean the rented house where the murder took place, Barber and his daughters, who had been staying with their aunt in Arlington, moved back into the house.

But after a month surrounded by memories of his wife, Barber said he moved to a townhouse in the country.

Six months later, Barber said he "found that taking care of them was killing me." He said he did not make enough to continue to send his daughters to the Congressional School, a private Fairfax school and to hire a woman to take care of them at night.

"I thought I could do it with the kids. I didn't realize what a woman and a wife does. Not just running a house. I couldn't give them a female presence, a female understanding."

He sent the girls to Durham, N.C., to their maternal grandmother. But Barber, a computer salesman, was transfered to Florida a year later.

Kimberly, who went to a psychiatrist for six months after the murder, cries at the mention of her mother's death. Her father says that she has had trouble adjusting and that he's frightening by what her memories of the murder will do to her as an adult.

"I feel horrible about not having a mother," Kimberly said. "I don't have anybody to turn to when I'm in a jam." Referring to the murder, she said, "I understand only that I'm not going to see her again."

Relatives of the victim say their hatred of the murder has been inflamed by recent news that Voetsch has not spent a day in a state prison, although he was sentenced to "15 years at hard labor" for second-degree murder. The victim's relatives say Voetsch lives a "country club" life in the Fairfax County jail, where he serves as a cook.

Barber and Nancy Vardakas, a sister of the victim, say they see no justice in Voetsch's confinement. Their anger led them to urge a reporter to interview Kimberly about her mother's murder, even though they said they anticipated her pained and tearful response.

"It never ceases, the pain and horror of it. At anniversaries and birthdays it get worse. When it comes out that he is not being punished like he should be, the only thing you want to do is scream," said Colleen Smith, the aunt who lives in Arlington.

Faye Bagley, 65, the girl's grandmother in North Carolina, suffered a stroke this spring and is hospitalized. The girls, now in Arlington with their aunt, will move at the end of the month to Florida to live with their father.

Barber now is planning to hire a woman to take of them in St. Petersburg. "This murder," he said, "has just ripped all the roots out of the children. They don't know where their home is."

Psychiatrists who have examined Voetsch since the murder and sheriff's deputies who know him at the jail say he is well-adjusted and normal. Voetsch told a pyschiatrist soon after the murder that "little voices" had told him to get even with people he thought were making fun of him.

But when he was sent for examination to Southwestern State Hospital in Marion, Va., Voetsch admitted he had made up the "little voices" story because he was frightened. "You know, cop an insanity plea and all that."

The murder, Voetsch said, humiliates and confuse him. He said he cannot belives that he was the man who did it. "It always stands out in my mind as something horrendous. I can't dismiss it. They (the family) must really hate my guts."

Arthur Voetsch said he has wondered if he pushed David too hard when he played Little League. Both parents said that after years of examining what possible mistakes they could have made raising David, they've decided the murder was not their fault. "We don't carry the burden anymore. Our only worry is our son. We just want to get him home," Lois Voetsch said.

In Shrub Oak, a suburban community of about 20,000 people where th Voetsch family is well-known, the Voetschs say friends have helped them get over the shock of the crime. More than 400 people signed petitions sent to Fairfax County Circuit Court attesting to David Voetsch's good character.

Voetsch's parent say they both pray for Rebecca Barber's children. "Every Christmas we ask ourselves how are those little girls doing," Arthur Voetsch said. "It was a horrendous thing that happened."

After their son's trial in Fairfax County, Arthur and Lois Voetsch were approached in the courthouse hallway by Nancy Vardakas, the victim's sister.

Lois Voetsch said she was nervous because the woman looked upset. "I didn't know what to say to this woman," Mrs. Voetsch recalled. Nancy Vardakas remembered she saw in Mrs. Voetsch's eyes fear, fear of vengeance. Arthur Voetsch ended the confrontation by putting his arm around Vardakas and saying he was sorry.

Voetsch works and lives in the work-release section of the county jail, a section where the doors was unlocked during the day. It is a section normally reserved for county prisoners with less than 120 days left to serve in jail.He did not go to a state prison because Fairfax County Sheriff James D. Swinson requested in 1975, that he be kept at the jail.

Swinson has said he keeps Voetsch in the jail because he is both a good cook and a responsible inmate. "This boy comes from a fine family. Just because a man is charged with murder doesn't mean he is all that vicious."

Voetsch calls the work-release section of the jail where he recently moved "Paradise," mentioning his freedom to move around the halls and activity room in the work-release area. He has a private room, although it is narrow and has no windows, and access to a table tennis set and color television.

David Voetsch said last week he is grateful to have avoided the state prison system where he says there are "pressures" that would interfere with his goal of proving to a parole board that "I'm worthy of being on the outside."

This month Voetsch became eligible for parole, but the parole board denied his request because of the seriousness of his crime. Next June, he will apply again.

"For what he did," argues Horan, who objected to Fairfax County Circuit Court Judge Barnard F. Jenning's decision to allow Voetsch to plead guilty to second-degree murder, "parole would be a disgrace." It would set an ultimate for the cheapness of human life."

Nancy Vardakas, the victim's sister who lives in Brooklyn, said she has relived the murder on scores of Saturday nights. She says she has prayed that her sister lost consciousness during the struggle, that she was not tortured. She says she cannot understand why a man who killed her sister could be set free.

The little girls, Voetsch said, are often on his mind. "Growing up without a mother really bums me out.

"I have a really good family behind me. They are behind me all the way, helping me out. I can't conceive of life without them."