The police and prosecutor of Prince William County differed sharply yesterday over whether they have a "prime suspect" in the slaying of three young women in a Dale City trailer a year ago this month.

Prosecutor Paul Ebert told reporters that a man he described as a construction worker in his late 20s who lives outside Prince William is the leading suspect in the highly publicized case. Ebert expressed confidence that the man would be charged with murder "sooner or later."

But county police Major E. A. Grove said flatly yesterday, "There have been no breakthroughs."

"I think Paul must have made a political speech somewhere last night," Grove said after being deluged with inquiries concerning Ebert's announcement that a suspect had been found.

Ebert, a controversial part-time prosecutor who is running for reelection next fall, said the man has been a focus of the police investigation since last summer and was known to have been in the vicinity of the crime at the time. He said police have interviewed the man repeatedly.

Grove contradicted that account, saying the investigation "has several suspects. We are not aware of what he (Ebert) is talking about."

The bodies of Deborah Warner Frank, 23, of Alexandria; Sharon Lake, 25, of Dale City, and Karen Rose Scarborough, 17, of Falmouth were found June 26 lying side by side in a trailer used by Ryland Homes as a sales office. All three had been shot in the head.

Scarborough was spending her first day on the job as a Ryland Homes receptionist when the murders occurred. Lake had accompanied her friend Deborah Frank to the trailer on a house-hunting trip.

Police said none of the victims had been sexually assaulted, a total of about $30 was missing from the women's purses, police estimated.

The police have since conducted what Elbert called "the most extensive and expensive investigation" in the county's history, although neither Ebert nor Grove would give a precise figure of the cost.

Two investigators, Wilson Garrison and William Methany, supervised by Sgt. Harold Morgan, have worked full-time on the case for a year. They have interviewed more than 2,000 people according to Ebert.

Ebert said yesterday he believes the man he regards as the main suspect will be charged, but acknowledged there is a "possibility" that the case will remain open forever because of insufficient evidence.

"It's one thing to feel you have the individual and another to be able to prove it. Until the loose ends are wrapped up we'll be unable to make a charge," he said.