Within hours of the 1995 murder of Anne E. Harper, Fairfax County homicide detectives felt all signs pointed to one suspect: her younger brother, Matt. But signs don't always translate into evidence in a courtroom, so Detective June Boyle kept digging. And digging. And digging.

It took nearly three years before Boyle convinced prosecutors that she had enough proof to charge the clean-cut college student with murder. And after Matthew Harper finally looked at that proof himself, he admitted stabbing his 20-year-old sister to death, then received a 35-year sentence.

Gradually, Boyle had solved one of the county's most sensational murders. Yesterday, her tenacity was recognized when she received Virginia's "Top Homicide Investigator of the Year" award at the annual meeting of the Virginia Homicide Investigators Association in Williamsburg.

Boyle, 44, is the first woman to win the statewide honor and was also the first female homicide detective in Fairfax. All this from a Boston native who never really gave much thought to a career behind a badge.

"I had no plans to be a cop," Boyle said. "I knew somebody, one of my neighbors [who was an officer]. I needed something exciting. I was 20. I thought it would be exciting."

And the dangers of patrolling the streets and capturing killers? "I never thought about it," Boyle said, with a veteran cop's nonchalance. "It hasn't been dull."

After five years in a police cruiser in the Franconia district, Boyle moved up to detective and spent much of the mid-1980s in the narcotics bureau, using her distinctive New England accent to persuade drug dealers to sell dope to her.

But she was more than just a druggie decoy. She also backed up fellow detectives, and in November 1987, Boyle shot and killed an apparent drug dealer. Boyle's partner had just bought an ounce of cocaine from a man in a pickup truck near Bailey's Crossroads, and when Boyle moved in for the arrest, the man suddenly bounced up from behind the dashboard. Boyle, surprised, reflexively fired once and fatally wounded the man in the head.

"If I didn't shoot him, I thought he was going to shoot us," Boyle said. The man was unarmed, but Boyle eventually was cleared of both criminal charges and of liability in a civil lawsuit.

Boyle became the first female robbery detective in 1992, moved to sex crimes in 1994, and was loaned to the homicide unit on Thanksgiving morning of 1995, when Anne Harper's body was found in the living room of her family's heavily burned home south of Fairfax City. Harper's mother and grandmother narrowly escaped the fire, while Matt Harper, then 18, spent the night at his girlfriend's house.

"We had to go through many other leads," Boyle said. "Matt could never be cleared. The other suspects could be cleared."

But the fire, which Matt Harper later admitted setting, created a confusing crime scene, and the knife used for the murder had been burned. While Boyle waited for lab tests, she began digging through Matt Harper's past. Eventually, she learned that Harper had successfully submitted phony insurance claims and that he knew of his beneficiary status in a family life insurance policy.

Boyle also began repeatedly visiting Harper's girlfriend, hammering away for small details about Harper's behavior the night of the murder. In time, the young woman helped lead police to a pair of discarded shoes with human blood on them, which police believe Harper had thrown away after the killing.

When lab tests showed that Anne Harper's blood was found on her brother's jeans, and on the outside of the front door to their house, Boyle confronted Matt Harper. He had no explanation. Later, after Matt Harper enrolled at James Madison University, Boyle traveled to Harrisonburg with a search warrant to help take Harper's footprints in hopes of matching them to the discarded shoes.

As the case grew nearly two years old, Boyle re-contacted Anne and Matt Harper's friends. "By now," Boyle said, "people who believed in the Harpers are becoming suspicious and talking to us." Boyle also noticed that Anne Harper's mother and her brother seemingly had little interest in helping Boyle find the killer. The Harpers' attorney, Arthur M. Schwartzstein, declined to comment on the case.

By the summer of 1998, Boyle had finally persuaded Deputy Commonwealth's Attorney Raymond F. Morrogh to charge Harper. She feared witnesses would soon forget their facts. Harper was indicted for murder in September, posted bond and returned to college.

Boyle kept plugging. Not long after the indictment, she located the Harpers' former maid, who told her of Matt Harper's explosive temper. And in a final confrontation with Harper's former girlfriend, Boyle extracted a final strand of damaging testimony.

"She didn't wait for the leads to come in," homicide Lt. Bruce Guth said of Boyle. "She went out and found leads. She got a lot of help, and it was a priority case for us, but June kept it at the forefront of the squad."

Boyle, who also was named "Policewoman of the Year" in 1995 by the Mid-Atlantic Women's Law Enforcement Association, was one of three homicide investigators honored yesterday by the 580-member statewide group. Fairfax Detective Robert Murphy won the award in 1995.

CAPTION: June Boyle, 44, the first female homicide detective in Fairfax, is the first woman to win the statewide award.