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Police solve 1975 cold case involving murder, sex assault of 19-year-old woman

Grand Junction Police said they built a DNA profile and traced it back to Jimmy Dean Duncan.
Credit: Grand Junction Police Dept.

GRAND JUNCTION, Colo. — On Dec. 27, 1975, 19-year-old Deborah Tomlinson was found dead inside an apartment in Grand Junction. 

Now, police said they've solved her murder.

Tomlinson was found in an apartment in the 1000 block of Belford Avenue, which is just south of Colorado Mesa University, Grand Junction Police (GJPD) said.

She had been sexually assaulted, bound and strangled to death, police said.

Investigators said they gathered evidence and performed interviews with neighbors and possible suspects, but weren't able to find enough evidence to charge a suspect. The case then went cold.

In 2019, GJPD re-looked at the case with new eyes. 

Earlier this year, homicide investigators asked for a Virginia-based company's services.

Parabon Nanolabs has a DNA analysis service called "Snapshot" that other law enforcement agencies have used before after exhausting other traditional DNA methods, GJPD said.

Parabon created a genetic profile from Tomlinson's crime scene by comparing it with a public genealogy database, hoping to find people who shared DNA with Tomlinson's killer.

From there. family trees were built and newspaper obituary archives and other public records were scoured to narrow down possibilities before a final list of leads was issued, police said.

After receiving the final list of leads, Grand Junction Police investigators continued the investigation. leading them to identify Jimmy Dean Duncan as Tomlinson's killer.

“Cold cases are never truly closed,” Grand Junction Police Chief Doug Shoemaker said. “Solving these types of cases is very important to our detectives and our agency, and while not every case is solved, we are proud of the hard work put forth by those who helped provide answers to the victim’s family and our community in as many cases as is possible.” 

Police said investigators got a DNA swab from one of Duncan's relatives and submitted it to the Colorado Bureau of Investigation (CBI) for comparison with the original DNA evidence.

CBI confirmed that Duncan was Tomlinson's killer after analyzing the DNA according to Parabon's Snapshot parameters, police said.

Duncan had not been identified as a suspect during the initial investigation, police said.

Duncan, a Colorado native who was 26 years old at the time of Tomlinson's murder, died in 1987.

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