18-year-old Traci Hammerberg was murdered in a town outside of Milwaukee 35 years ago

Traci Hammerberg
Credit: Ozaukee County Sheriff's Office

Milwaukee-area authorities announced on Tuesday that they had solved a 35-year-old murder using information from a genealogy database.

In a press conference on Tuesday, Sheriff James Johnson with the Ozaukee County Sheriff’s Office said that the 1984 murder and rape of Traci Hammerberg in nearby Grafton, Wisconsin, had been solved, according to the Milwaukee Journal Sentinel.

Johnson identified Philip Cross, who died of a drug overdose in August 2012, as the suspect. Cross was 21 years old and living in Wisconsin at the time of the murder.

“After almost 35 years, we found the person that had brutally raped, strangled and bludgeoned Traci Hammerberg to death,” Johnson said.

According to Johnson, Hammerberg was found by a hunter at 5:45 a.m. on Dec. 15, 1984. She was naked from the waist down. Earlier in the evening, Hammerberg had gone to a babysitting gig and attended a party with her friends. She left the party alone on foot.

“Autopsy finds revealed that Traci had been sexually assaulted and strangled,” Johnson said. “She had been repeatedly struck on the right side of her head with a metallic object … She was brutally beat.”

Using semen found in Hammerberg’s body and DNA found underneath her fingernails, authorities created a DNA profile of her attacker, but were unable to identify him at the time.

In the 35 years since, the Ozaukee County Sheriff’s Office worked in partnership with Wisconsin’s Department of Justice Division of Criminal Investigation and the FBI Behavioral Analysis Unit to identify the DNA profile, Johnson explained.

Earlier this year, investigators decided to focus on forensic genealogy and the DNA profile was updated to a genetic genealogy database in order to identify family members of the suspect. The closest relative that the database found was a second cousin, Johnson said.

“The next step of the process was to start building family trees back four generations,” he explained. “We then filled in the family genealogy to the current generation to encompass any male that would have been between the ages of 16 and 60 in 1984 … then returned to a traditional investigation of locating and eliminating these suspects.”

In August, Cross was identified as a potential suspect. Days later, after sending Cross’ DNA — from the medical examiner’s office — to a lab, investigators confirmed that the DNA profile developed from Hammerberg’s body matched Cross’ DNA.

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“Philip Cross had a violent temper and was known to act violently when he did not get his way,” Johnson said, adding that Cross rode the same bus as Hammerberg to school.

Genealogy databases have recently been used by authorities to solve decades-old crimes, including those of the suspected “Golden State Killer,” who is believed to have committed at least 13 murders and 50 rapes across California throughout the 1970s and ‘80s.