The case against Joseph O'Brien, a 27-year-old Arlington man charged in the stabbing death of a 55-year-old neighbor, will be a "patchwork quilt" of circumstantial evidence, the prosecutor said yesterday at the opening of O'Brien's trial.

"This is an incident, as you will hear, that involves just two people," Arlington Commonwealth's Attorney Henry E. Hudson told jurors in his opening statement -- "Mrs. Betty Jane Konopka and the individual who broke into her house that night -- and Betty Konopka isn't here to testify."

Konopka, a widow who lived alone at 130 S. Woodrow St. and was a secretary at the Labor Department's Office of Mine Safety and Health Administration, was found nude on her bed by a coworker on June 6, 1984.

She had been stabbed 19 times, a medical examiner's report showed.

O'Brien, who lived near Konopka in the North Barcroft neighborhood, was indicted in July on charges of capital murder, robbery and burglary. The maximum penalty for capital murder in Virginia is death.

After jurors were selected yesterday, Hudson outlined the evidence he will present -- primarily the results of laboratory examinations of blood, hairs, glass fragments, threads and shoe prints found in Konopka's house.

"The commonwealth's case is going to be much like a patchwork quilt . . . . When all those patches are in place, I'm going to ask you to find Mr. O'Brien guilty of capital murder," he said.

Court-appointed counsel Brendan Feeley told the jurors that O'Brien, who he said had cashed two large checks the day before Konopka was killed, would have had no motive for robbing her.

"I believe you will find that the evidence the prosecution is required to produce does not constitute enough for a conviction," Feeley said.