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A cigarette butt proved to be the undoing of a man suspected of killing a girl in Utah 18 years ago, after a sheriff trailed him for four days to grab the DNA evidence.

Without the efforts of Wasatch County Sheriff Todd Bonner, the case would have been forgotten long ago. For Bonner, however, it was personal. As the original investigator in the bludgeoning death of the teenage prostitute in 1995, he couldn't let it go.

"It was haunting me my whole career," Bonner told The Associated Press on Friday. "It doesn't matter that she was a street girl. This is a 17-year-old girl — a human being. I could care less what she did for a living. She was doing what she had to survive."

The body of Krystal Lynn Beslanowitch was found Dec. 6, 1995, along the Provo River near Midway.

Bonner said Joseph Michael Simpson, who was arrested Tuesday, was "never on our radar" until earlier this year, when a lab extracted "touch DNA" from the granite rocks used to crush the teen's skull.

Bonner flew to Sarasota, Fla., to help arrest the unemployed 46-year-old, who was living with his mother there.

A convicted murderer, Simpson had been paroled from Utah State Prison months before Beslanowitch's slaying and probably encountered her on a gritty Salt Lake City street. A shuttle-bus driver for a Utah resort, he would have been familiar with the area around Midway, a mountain town 38 miles southeast of Salt Lake City where she was killed, Bonner said.

Beslanowitch, originally from Spokane, Wash., had been in Utah for five months before her death.

Jeff Beslanowitch, a retired 61-year-old steelworker from Spokane, told the AP that Krystal Beslanowitch was a runaway daughter of his ex-wife, but no blood relation to him, and she "never had a chance in life."

"Krystal had a troubled upbringing with drugs and prostitution. It was quick, easy money," Jeff Beslanowitch said Friday. "I'm glad they got him. It took a long time, but this guy deserves to sit in a cell for the rest of his life."

After years of dead-end leads, improved DNA technology let investigators finally get a full match on Simpson in January from evidence at the rural crime scene.

Salt Lake City-based Sorenson Forensics found Simpson's full DNA on a spot where he had touched one of the granite rocks. The process of collecting it, using a vacuum-assisted instrument, took a full day.

"In forensics, that's fairly new technology," said Cami Green, once a DNA analyst and now a sales manager for Sorenson Forensics. "It is the most sensitive collection method we have at our disposal."

Authorities already had a DNA sample from Simpson from his earlier incarceration, but prosecutors insisted that Bonner retrieve a fresh sample for a match.

The sheriff stalked Simpson with the help of Florida detectives for four days earlier this year. At first, they were hoping to retrieve a glass or spoon he might leave at a restaurant. Instead, Bonner grabbed a discarded cigarette Simpson left at a smoke shop in Sarasota.

Florida law wouldn't give Bonner enough time to arrest Simpson first and then process a DNA sample later, so they had to grab a sample surreptitiously, the sheriff said.

The 350-pound suspect was chatty during his arrest but refused to say anything about the slaying, Bonner said.

Simpson, formerly of Clearfield, Utah, is being held on suspicion of aggravated murder. He has waived extradition and will be brought to Utah within weeks. Bonner expected charges to be filed soon in Utah's 4th District Court.

Bonner credited his detectives "for solving this case for me. They deserve the credit." A year ago, he assigned Detective Brian Gardner to work it full-time.

Krystal Beslanowitch was buried long ago in Spokane, Wash. A message left Friday for her mother wasn't returned.