A young Houston private eye on her first case befriended a suspect in a three-year-old murder case, dated him for 2 1/2 months and told him she couldn't consider his marriage proposal until he revealed the dark secret he'd hinted he was carrying.

The prospective bridegroom bared his soul Thursday night, not knowing that Kim Paris, 23, was a detective and had a tape recorder in her purse.

When the suspect had confessed all, Paris said, she told him she needed a cigarette, and they drove to a convenience store. She got out of the car. It was the last he saw of her.

Moments later, police officers who had been monitoring the conversation swooped in and charged the dumbfounded man, David Duval West, 28, with the 1982 killings of a prominent Houston lawyer, James Campbell, 55, and his wife, Virginia, 50. They were shot in their sleep as two of their grandchildren slept at the foot of their bed.

Police say one of the Campbells' four daughters, Cynthia Helen Ray, prevailed on West, her boyfriend at the time, to kill her parents so she could collect her share of their estimated $2 million estate. Ray was charged Saturday with capital murder.

The Campbells' other three daughters hired Clyde Wilson Investigations late last year. Wilson said Ray, known as the family's "problem child," and West were suspects from the start.

"But he certainly wasn't going to sit down and spill the beans to me or one of my men," Wilson said of West. "It seemed like the logical thing to do was to bring the girl into the case to gain his confidence -- which she did, fabulously well."

Paris, a dentist's daughter and former naval air-traffic controller, had worked less than a year in the agency's insurance-fraud division, surreptitiously videotaping accident victims who claimed that they had been incapacitated.

After veteran detectives gave her "intensive coaching and moral support," she insinuated herself into West's life with a gambit any detective-story buff could have spotted a mile away.

Paris knocked on West's door one evening and feigned embarrassment when his roommate told her that the person she was looking for didn't live there. She asked if she could use the phone. She struck up a conversation. That night she spent three hours with West and his roommate at a bar.

"Between you and me," she said in a telephone interview, "I've never had much difficulty approaching somebody I want to get to know well."

Paris said she and West saw each other "about three or four nights a week" thereafter. The relationship, she said, was strictly platonic.

"I kept dancing around that subject sex . . . . ," she said. "Actually, it wasn't that hard. He fancies himself an intellectual, being on a higher plane than most people. David and I spent a lot of time discussing history and politics and religion." West, a delivery boy for a blueprint company, is a survivalist and a gun collector and reads Soldier of Fortune magazine.

When he proposed, Paris encouraged him to tell her the "awful" thing about his past to which he had alluded in earlier conversations. At that point, the detective agency contacted police and the district attorney's office, and Paris was given the tape recorder. The sting came off without a hitch.

Wilson said he has spent so much time "bragging on" Paris in the past two days that it was difficult to have to "scold her for one slight indiscretion, but I did, anyway . . . .

"She made a flip remark to one of the local TV reporters after the arrest, something to the effect that, 'Well, I guess this means I won't be going to meet David's mother Sunday night.' That was unprofessional, and I told her so. We have nothing but sympathy for the boy's mother," he said. Nonetheless, Wilson is rewarding Paris the way he rewards all his detectives when they crack their first big cases -- with an inscribed, pearl-handled pocketknife. "I guess I'll also be hiring a new video cameraman," he said.

For her part, Paris said, "This whole thing was very emotional for me. You can't be involved with someone for 2 1/2 months under the circumstances that I was without there being real ties. I spent 2 1/2 months inside his head."

Does she have any regrets? "I have no qualms about what I did, no," she said.

Meanwhile, of the many congratulatory telephone calls Wilson fielded today, one came from -- who else? -- a Hollywood agent