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More than 100 unsolved murder cases are tucked away in the files of the Salt Lake City Police Department.
Though many are rich with evidence, they often lack the definitive link between victim and suspected attacker. But a recent development in DNA testing has helped make the link. This month, such testing has helped put three men behind bars in connection with murder cases that had gone cold for years.
The arrests promise to bring some measure of relief to the victims' families.
And they illustrate how - more than 100 years since fictional sleuth Sherlock Holmes popularized forensics - science continues to advance the work of solving crimes.
The new DNA technology, known as Y-STR, has been available for a few years but has only recently been available in Utah, says Tim Kupferschmid, director of Sorenson Forensics in South Salt Lake.
Opened in November, the Sorenson lab is the first in the state to use the new method, which singles out the Y chromosome - effectively linking skin cells, hair, blood or other DNA evidence specifically to their male owners.
This science was effective in filing charges against 40-year-old Michael Jones in the murder of Tara Brennan, whose body was found in her car at Salt Lake City's Poplar Grove Park on Feb. 24, 2004. Brennan was found with a belt around her neck and stab wounds on her neck and face, according to court documents.
Salt Lake City Police Chief Chris Burbank says his detectives constantly are examining the evidence in unsolved murders in relation to how new technology can be applied.
With the hope of finding something new, detectives submitted Brennan's evidence for review in November, along with evidence collected in the slayings of Cathy Cobb and Tiffany Hambleton. Though the process can be difficult, the results were almost immediate, Burbank says.
Traditional DNA testing - called STR analysis - is effective in matching cells with one another but can require an overwhelming amount of work to find the right match among the multitude of cell evidence. The new Y-STR analysis eliminates the needle-in-a-haystack effect by illuminating male DNA.
This method can be particularly effective in cases with female victims because a man's DNA found on a woman's body or in proximity to the murder scene will stand out, Kupferschmid says. Once the male cells are identified, it is up to the police to provide the suspect's DNA, which can be matched by the lab using the more traditional STR analysis.
The three cases this month that identify suspects are likely just the beginning.
"We are working on cases with law enforcement throughout the valley," Kupferschmid says. "Hopefully, it will spread throughout the state."
In Brennan's case, the Y-STR testing found male DNA evidence on a cigarette butt found in her car and also on the belt and ligature markings on her neck. It was later linked to Jones, according to 3rd District Court documents charging him in connection with first-degree felony murder.
Among the millions of cells packed beneath the fingernails of 14-year-old Hambleton, who disappeared in February 1986, DNA analysts at Sorenson recently found genetic markers that allegedly matched those found in blood samples taken from 44-year-old Dan Peterson.
Hambleton was last seen with Peterson, who has denied any knowledge of the girl's death. First-degree felony murder charges were filed against Peterson on Jan. 12. He was arrested a few days later in Phoenix.
Similar science was used to charge 51-year-old Michael Johnson in the death of Cobb, 40, who was strangled Jan. 11, 1998. Johnson's DNA was found on fingernail clippings taken from Cobb during the investigation. Johnson was charged Jan. 8 and arrested a short time later.
Burbank says the crime-solving possibilities are endless with the new testing.
"It's really exciting," says the chief. "And it's amazing you can come up with some of these things after 21 years."
Both Kupferschmid and Burbank were hesitant to openly discuss the cost of the test, which is not currently available at the Utah Crime Lab. Kupferschmid acknowledged that the new method is expensive, and Burbank called the potential impact to the department's budget significant.
"If we can bring closure to some of these families," Burbank says, "that's what we should be doing."