Two years ago today, Judith DeMaria left the Capitol Courts Club in Sterling, where she worked as an instructor, went for a late morning walk on the Washington and Old Dominion bike path, and didn't come back.

Several hours later, a worried friend at the club called the police. At 10 that night, the case went to Robert E. Turner, then a Loudoun County deputy sheriff. For the next two months he worked only on that case, tracking every lead, talking to her family and friends. Sometimes he would just drive out to the bike path where she was last seen and sit in his car and -- think, watch, wonder.

He believes that Judith DeMaria is dead. And he thinks he knows who killed her, although he has never been able to make an arrest.

By the fall of 1985, he had to put the DeMaria case on a back burner, but it is still open and he still thinks about it and watches the teletype wire for reports of bodies that can't be identified.

Bob Turner is not romantic about his work. His sentences are short bursts of thoughts, direct, to the point, sometimes funny. But when he gets going in conversation, there is fire and energy, a little swagger too. And now, two years later, he says of the case, without elaboration, "It's the best one I've ever had."

Technically, he's not a criminal investigator anymore. Now a corporal, he supervises uniformed street officers. But he still carries DeMaria's driver's license. It has a picture that maybe someone can identify.

And when you call to ask if the police are still looking for Judith DeMaria, he says without hesitating: "Hell, I'm still looking."

In one dream, he sees her walking by. In another dream, he finds her body.

"Who knows? Dreams are crazy," Loudoun County Police Investigator Jay Merchant says, dismissing them.

"Sometimes I'd just wake up in the middle of the night and then I'd lay there running all this stuff through my head -- 'What else can I do? What have I overlooked?' "

Merchant was called in to work with Turner two days after DeMaria disappeared. It is still technically his case -- although he says that if something compelling occurs, he hopes that Turner would be brought back on -- and he describes his feelings for it as a mixture of personal commitment and professional fascination. "Obsessed may not be the word," he says. "But you get a personal feeling for it. It's not just a job."

Then there is the sense of putting something to rest. "I really believe she's dead," Merchant says. "And I would really like to be able to go to {her family} and say she's dead and the reason why I can say that is because we found her body . . . I know how people are. It's no different from people having someone in Vietnam listed as a missing person. They're always hanging onto that hope that, hey, maybe some day word's going to come that this person lived through it . . .

"As long as the family thinks there's any chance I think it's just human nature to do that. But as long as that's there, I don't think the family of the people who have that hope can really get back to everyday life.

"Plus," he says, "I think the guy who did this to her ought to pay his dues."

Vanished Footsteps The trail runs for miles, from Alexandria to Bluemont, one long path through rolling, often desolate land, a rural vestige of fast-developing Loudoun County.

As you travel west from Route 28, the slope of the trail rises, making a 15-foot grade above the land to the south. She was just crossing the bridge that runs over Broad Run Creek when workmen in a truck passed. They are among the last -- along with a woman riding a bicycle on the path -- to have seen her.

On the north side of the trail, in some parts beyond the bridge, there is a curtain of trees and bushes dividing the path from an empty field that stretches for miles.

The first time Turner walked the trail was two years ago, at dawn on a Saturday -- a continuation of his Friday night work -- and he didn't notice the blood in the field. That was discovered later in the day. Three pools of human blood -- too much for someone to have lost and survived without medical attention. It turned out to match DeMaria's blood type. (It's impossible to know if that was definitely DeMaria's, although Turner and Merchant are convinced that it was.)

Today, faded orange plastic markers still flutter on bushes near where the blood was found. Turner spent hours in the field, searching on his hands and knees, trying to reconstruct what had happened, brooding over the distances from the trail to one bloodstained spot to the next.

Near all this, sunglasses thought to be DeMaria's were found and there was an imprint in the grass as if someone had been sitting there. Turner's construction: She was hit at one spot, dragged behind the trees and moved perhaps once more before the murderer returned to move her body to a vehicle. A music headset thought to be DeMaria's was found a half mile northeast of the bloodstains.

Turner went back again and again to the trail. The first week of his investigation, he went every day. "I'd go out there about 12 o'clock and stay until about 1:30 or 2. Nobody. I almost scared myself one time. I got there and the wind started blowing and the clouds started rolling in and I thought, 'Wooo! Let me get of here.' "

Turner observed what times people passed on the trail and how far they went. "Most people will run down to that bridge, turn around and go back," Turner says. The blood was found about a quarter of a mile past the bridge going west.

DeMaria's exercise was walking fast -- "about an 11- or 12-minute mile" Turner estimates. From a distance, a casual observer might have thought she was jogging. She did this every Monday, Wednesday and Friday, Turner says, sometimes turning back at the bridge, sometimes going farther.

The feeling is that DeMaria was murdered by someone who had also observed this. "Whoever was there knew that the people would only come to the bridge and go back," Turner says. "That's why everything was just a little farther out. They knew her patterns, they knew the patterns of everyone."

The Appalachian Search and Rescue Conference came with air scent dogs and searched 3,000 feet on either side of a two-mile length of the trail for two days. All they found was a marijuana patch.

It was disappointing but not surprising. Consider the 1986 disappearance of 19-year-old Cynthia Barrows in Annandale, says Turner, who's gotten to know a lot about missing-persons cases. "She was found only six miles from where she disappeared," Turner says. "The area that we searched extensively {for DeMaria} was . . . less than a mile {on both sides of the trail}." He suggests that even an extensive search could only have covered a fraction of the nearby territory.

Turner looks across the field. "You know what's really bizarre?" He tells you about a nearby construction site where 3-by-6-foot crates were used for shipping materials. "Well, they had one of those crates stolen a week before she came up missing."

Victim and Suspect Turner and Merchant know a lot about Judith DeMaria -- 5 feet 6 inches tall, 140 pounds, dark brown hair, brown eyes. She was 27 when she disappeared. She taught tennis at the club, and elsewhere she led exercise classes. "She was good at any kind of racquet sport," Turner says. Her car? "A white Datsun -- B210," Turner says. " '76, I think it was." Boyfriends? "Not that I could find." She lived with her dog, a dachshund, in her Manassas garden apartment.

When another jurisdiction called once with information about a body that might be DeMaria's, a description of the clothing and jewelry -- long, dangly earrings -- was given. "And as soon as I heard that I said, I almost bet you that's not Judi," Merchant says. "I just remember from what jewelry of hers I'd seen and what pictures I'd seen, I'd never seen her with long earrings."

They refer to her as Judi and speak of her respectfully. They didn't just know her, they liked her. She had battled with a weight problem, swinging down and up and back down again, they say. "She was at a low point in her life but was coming back up again," Merchant says. "She was becoming attractive to guys again. Maybe she hadn't fully realized it yet."

Her growing self-confidence was one of several reasons why Merchant never thought she planned her disappearance.

She left what Merchant calls "a substantial amount" of money in her savings account. And she missed scheduled appointments that Friday. "To just not show up at all, she just wasn't that way," Merchant says.

They searched her apartment, they listened to her answering machine, they checked her mail, they talked to her friends and family and neighbors. Somebody went through her apartment the Friday that she disappeared, and that person was later questioned, but Turner is noncommittal as to whether this was a lead.

"Every time someone would get arrested in another jurisdiction for something kinky, we'd talk to them, find out where they were, see if they were in the area," Turner says. There was the man in Montgomery County who was arrested after he broke into a woman's house and ran out wearing her underwear. When he said he'd been living on a bike path in Virginia, Montgomery County police were on the phone to Turner, who dashed over to talk to the man. "It turned out it wasn't the bike path he'd been living on, it was the Appalachian Trail," Turner says. "He was just a fruitcake."

And there was the woman in Gaithersburg "who swore up and down on a stack of Bibles that she'd seen her at one of the shopping centers," Turner says. After talking to her, he concluded, "Mistaken identity."

And the psychics: "You have to listen to them," Turner grumbles. "You never know."

They both think they know who killed her. And they're certain that the suspect, a man, knows he's suspected. But there's been little the police could do about it. "We don't have the evidence to arrest him," Merchant says.

"I guess it wouldn't be fair for me to say I totally absolutely know, yet I really do feel that this guy is the suspect who did it," Merchant says. "But like I say, I would never not continue to look at whatever comes in. Obviously I would like to look at the body. I hate to put this in print -- I guess I never really realized how important, how the body itself does tell you about the person you're looking for.

"I just think that this suspect -- I think he did it. But again, obviously I can't give a good reason why I do. I'll put it this way -- until someone else better comes along that would change my mind, I think this guy did it."

Their suspect lives in the area and knew Judith DeMaria. "I do keep track of him," Merchant says.

Turner says he was convinced early in the investigation that it was this particular man.

"He's obsessed with women," Turner says. "Ever met a psychopath? Besides he told me he did it. But not in so many words."

In fact, Turner says his intense concentration on the suspect brought on some departmental criticism. "There're a lot of things I wanted to do on the case that they wouldn't let me do," Turner says. "They wouldn't let me work the guy the way I wanted to. They said I was too narrow. I should be broad . . . I got yelled at a couple of times: 'You're going to have to get off of that guy. You don't have any proof.' 'You won't let me find any proof!' " Turner chuckles ruefully. "I was hot," he says confessionally.

From his perspective, he came so close. During one interrogation session with the suspect, Turner says, "I thought any minute now, he's going to confess. He was crying, his voice was shaking."

Turner says that during another conversation, the suspect said that he, himself, wanted to find out who had done this to DeMaria. " 'I just want five minutes alone with this guy,' " Turner quotes the suspect saying. Turner says he responded, " 'You probably spend more time with him alone that anyone else.' "

"If he's done it once he's certainly capable of doing it again under the right circumstances," Merchant says. "The only thing that might tend to change that would be in his mind he's got to be thinking, hey, if he ever got in the same situation again, became a suspect again, how much more pressure would be on him."

The Waiting Turner is 33, a former correctional officer and deputy sheriff in Arlington County. He likes to fish. And here's his philosophy of the street:

"I saw something in a John Wayne movie once -- 'Big Jake'," he says, "where his little grandson says to him, 'I'm scared,' and Big Jake says, 'So am I -- but don't let anyone know it.' That's the way I try to be."

Merchant, 45, retired several years ago from the Fairfax County police force after 20 years. A desire to get back to investigating work drew him to Loudoun County. He's always liked police work, but with investigations the challenge is exquisite. "The crime's already occurred," he says. "You come in after everything has happened and try to gather evidence. You try to fit the pieces together. I like puzzles and crossword puzzles and word games."

Apart from the DeMaria case, there were four murders that Loudoun County police handled in 1985. Only the DeMaria case remains unsolved. It's frustrating, Turner concedes. It's as if they could give you the structure but not the pieces.

"It's a makable case," Turner insists.

John DeMaria, the father of Judith DeMaria, says that he and his wife Martha Whitestone (Judith DeMaria's stepmother) "appreciate everything the police have done."

He shares the frustrations of the police. "I'm disappointed that there's not been a solution -- or resolution," he says, "but I can't fault the police in any way."

The only thing that haunts him is whether the police should have started their search earlier. "If a search had started immediately, something might have turned up . . . I think that's more a matter of technicalities. There was not a lack of willingness on anyone's part. I think Judi was beyond help almost immediately. We don't hold any grudges."

Judith DeMaria's close friend, Mary Lou Merchant (no relation to Jay Merchant), says she was "not all that impressed" with the investigation. "They're totally convinced they know who did it, and they're not looking anywhere else," she says.

Though the case is still open, most of what is left is waiting for new leads. "We sent fliers to every police department in the United States on Judi," Merchant says. "They're probably tacked up -- I like to think they're tacked up all up and down the country."

And there's a sense of waiting for time and circumstance to allow someone -- perhaps their suspect -- to reveal himself in some way. "I mean, this guy is doing other things, there's no doubt in my mind," Merchant says. "He may be a little more cautious now. He might not have actually killed someone else since."

Merchant wonders what goes on inside this man. "I have to believe sometime at night when he's going to sleep, it hits him," Merchant says.

Turner has from time to time driven by the bike path, not really looking for anything in particular. "It wasn't what I thought I was going to see," he says. "I wanted to make sure I wasn't missing anything."