Joseph F. O'Brien, a 27-year-old unemployed Arlington man, was convicted yesterday on a charge of first-degree murder in the stabbing death last June of his 55-year-old neighbor, Betty Jane Konopka.

An Arlington Circuit Court jury found O'Brien not guilty of burglary and robbery in the incident. The jury, which delivered its verdict after deliberating for nine hours, recommended a sentence of 50 years in prison.

O'Brien had been charged with capital murder and, if convicted of that charge, could have been sentenced to death.

Konopka, a secretary in the U.S. Labor Department's Mine Safety and Health Administration, was found in her house at 130 S. Woodrow St. early on June 6. She had been stabbed 19 times.

A glass pane in the back door had been smashed, and her wallet and keys were missing.

"We will definitely be appealing the case," defense counsel Brendan Feeley said after the verdict was read. "We are, of course, relieved that the death penalty is no longer a possibility."

Judge William L. Winston did not set a sentencing date; post-trial motions will be heard May 1.

The testimony against O'Brien, primarily from medical examiners, detectives and forensic scientists, was described by prosecutors as a "patchwork quilt" of circumstantial evidence unusual for a homicide case.

In closing arguments Friday, Arlington Commonwealth's Attorney Henry E. Hudson propped a chart before the jury listing the items he argued linked O'Brien to the murder -- including hair samples, a blue Velcro filament recovered from Konopka's bedroom carpet, footprints found on glass fragments in her kitchen and glass particles lodged in the treads of O'Brien's sneakers.

"It's important that you look at every item of evidence and its collective effect," he urged the jury.

O'Brien's court-appointed attorneys, Feeley and John Youngs, argued that such items of circumstantial evidence were not enough for a conviction. According to testimony, none of O'Brien's fingerprints was found in the house, nor any of his blood, and no blood from Konopka was found on his clothes.

Finally, Youngs argued, O'Brien had cashed two checks worth more than $300 the day before the murder, and thus had no motive for robbery.

O'Brien, who did not take the stand during the trial, sat impassively throughout the four days of testimony, occasionally writing notes to his attorneys or talking quietly with them.

The courtroom was crowded with neighbors, members of O'Brien's and Konopka's families, detectives, assistant prosecutors and court employes. But few spectators returned yesterday, and the verdict was read to a nearly empty gallery.

After it was read and each jury member was polled aloud, O'Brien lowered his head and pressed his hands to his forehead.

Under Virginia law, Winston may lower the jury's recommended sentence but not raise it. If sentenced to 50 years, O'Brien, who has served time in prison for grand larceny and unauthorized use of a vehicle, probably will be eligible for parole in 25 years, prosecutors said.