A year to the day after a Virginia state trooper was stabbed to death on the threshold of his Manassas town house, no arrest has been made, and investigators say the investigation has all but fizzled.

Police called the slaying of Trooper Johnny Rush Bowman on Aug. 19, 1984, one of the most savage and inexplicable in memory. Bowman was stabbed 42 times when he opened the door to his home about 4:15 a.m. His marked police patrol car was parked just yards away.

The killing touched off one of the most extensive and costly murder investigations in the history of the Virginia State Police, which has never let the killing of one of its troopers go unsolved.

Investigators set up a command center until Christmas in four adjacent rooms at the Manassas Holiday Inn. A handpicked team of more than 20 special agents followed leads around the clock.

More than 3,000 people in 41 states were interviewed by police, who pieced together Bowman's life and death in minute detail. Prince William County Crime Solvers offered a reward of more than $26,000 for information leading to the arrest of a suspect -- an inducement that still stands.

Today, police work on the case is sporadic, said Robert C. Martin, who heads the state police investigation. "I still feel very strongly it will be solved," he said, but acknowledged that his feeling was based on "a hunch," rather than on any leads investigators are pursuing.

"We have some people who qualify as possible suspects," said Prince William County Commonwealth's Attorney Paul B. Ebert. "But we're going to need a pretty good break in order to solve it."