In a quiet voice, Stuart L. Kreiner repeated the answer "guilty" three times yesterday in admitting that he stabbled to death three girlsa year ago in a wooded stream near their Anne Arundel County homes.

The guilty pleas by 17-year-old Kreiner brought to an abrupt close the case that began last October when the bodies of 10-year-old Debbie Hogan, her sister Terry, 8 and their 8-year-old playmate Ann Brzeszkiewicz were found in the woods about 100 yards from Kreiner's home.

Had the case gone to trial, the prosecution would have had to depend on Kreiner's father, Edward as a key witness - "the heart of the case," according to Deputy State's Attorney David R. Cuttler. Although it was the elder Kreiner who at first became suspicious of his son, and through a lawyer called police to his home, prosecutor's felt his further cooperatiion was "unpredicatable." This was one major reason they decided to accept the plea bargain, Cuttler said.

Although little was little was said at the yesterday's brief hearing before Anne Arundel County Circuit Court Judge Bruce C. Williams, a written statement of fact agreed to by Kreiner, his lawyers and the prosecutors told in detail of some of the events that began when the three girls ate a Sunday shrimp dinner at the Hogans' home last Oct. 9 and went outside to play.

The statement told of the parents' frantic search when the girl did not return home that night, and of the police finding their bodies in the shallow stream the next morning.Police also found an empty leather knife sheath nearby. It was on Oct. 10 after the elder Kreiner learned that a sheath was found at the murder scene and then noticed his own knife sheath missing that he first became concerned, according to the statement.

The next day, he noticed Stuart's red jacket "did not appear to be in proper condition," the statement asserts. He questioned Stuart, "who did not respond and began shaking uncontrollably," according to the statement.

Police were called to the Kreiner home, where they found a hunting knife and the red jacket, later found to be stained with blood. The elder Kreiner gave a statement, and his son was arrested.

Cuttler said he "theorized" that, Kreiner was playing with the three little girls, became angry with one of them and stabbed her. When the other two discovered what had happened, he stabbled them to avoid being caught, Cuttler believes.

The prosecutor said it is likely that Theresa Hogan, who would probably "freeze in terror at an attack," was the third victim. For this reason, the state sought a guilty plea to first degree murder, which involves premeditation, because "it is probable the defendant had sufficient time to reflect upon his action," in this case, Cuttler said. Kreiner pleaded guilty to second degree murder in the deaths of the two other girls.

Under the plea bargain, Kreiner will be sentenced to one life term and two terms of 30 years to run concurrently. He will be eligible for parole in 15 years.

The Hogan girls' parent, who watched yesterday's hearing from the courtroom's front row said they "have to accept the sentence, though we don't like it."

Ingrid Hogan said, "I feel he should be incaracerated for life." But she and her husband, Richard, said after long discussions in the past week with prosecutors they decided to accept the pleas because of the "unpredicability" of the elder Kreiner as a witness in a possible trial. Ingird Hogan said she would "have to rely on the parole board to make the right decision" in 1992 when Kreiner will first become eligible for a parole hearing.

As the hearing ended yesterday, Kreiner's father, mother, and older brother rushed to his side, and embraced him, as the slight teen-ager broke into silent tears.

Later, as Richard Hogan watched the Kreiner family descend the court-house stairs, he said, "I think it's better this way. What we just went through . . . in those few minutes in the courtroom. At least she (Mrs. Kreiner) could clutch her son, but we couldn't reach out and grab our two girls."