GRAND JUNCTION, Colo. — Detectives with the Grand Junction Police Department have solved the 45-year-old cold case homicide of 19-year-old Deborah Tomlinson.
On December 27, 1975 officers with the Grand Junction Police Department responded to an apartment complex located in the 1000 block of Belford Avenue. Shortly before 6:00 p.m. a call came into the dispatch center stating the body of a deceased female had been located inside one of the units. When officers arrived, they found 19-year-old Deborah Tomlinson, who had been bound, sexually assaulted, and strangled.
After reviewing all evidence, conducting witness and suspect interviews, and exhausting all leads and tips throughout a thorough investigation, detectives were unable to find enough evidence of who committed the murder and the case went cold. In 2019, the homicide case was given a fresh look by detectives and in 2020 the Grand Junction Police Department sought the services of Parabon NanoLabs, a DNA technology company in Virginia. Law enforcement agencies across the country use the company’s Snapshot ® DNA Analysis Service (Snapshot) to advance investigations when traditional DNA methods fail to produce a match. The newest Snapshot service offering, genetic genealogy, uses advanced DNA testing in combination with innovative genetic analysis, sophisticated identification techniques and traditional genealogical methods to establish the relationship between an individual and his/her ancestors. For forensic investigations, it is used to generate highly informative leads as to the possible identity of an unknown victim or offender.
In the investigation of the homicide of Deborah Tomlinson, Parabon analyzed a genetic data profile created from the unknown crime scene DNA sample and compared the results to a public genetic genealogy database, in hopes of finding individuals who share significant amounts of DNA with the unknown subject. These genetic matches served as clues to inform traditional genealogy research: first, familytrees of the matches were constructed back to the set of possible common ancestors using online genealogy databases, newspaper archives, public family trees, obituaries, and other public records, after which descendancy research was employed to enumerate the possible identities of the unknown subject. Other information, such as age, location, triangulation between matches, and/or ancestry and phenotype (trait) predictions, were used to narrow down the possibilities before a final list of leads was produced.
The Grand Junction Police Department then used traditional police work to continue the investigation whereupon Jimmie Dean Duncan was identified as a suspect. Our detectives subsequently acquired a buccal swab from one of Duncan’s known relatives and submitted the sample for comparison with the original DNA evidence that was found at the crime scene. The Colorado Bureau of Investigation confirmed that the newly acquired DNA profile positively identified Duncan using the parameters set by Parabon’s DNA Analysis Service, known as Snapshot. Duncan was not identified as a suspect in the homicide investigation prior to Parabon’s findings.
After receiving results from CBI, it was determined that Duncan, who was 26 at the time of the murder and a Colorado native, passed away in 1987. The family of Deborah Tomlinson was notified of the findings by the Grand Junction Police Department Detectives who worked diligently to solve the case.
“Cold cases are never truly closed,” said Chief of Police, Doug Shoemaker. “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.”