Genetic Genealogy Used To Crack 35-Year-Old Cold Case Of Murdered Teen

Traci Hammerberg’s killer has finally been found, decades after she went missing after walking home alone from a party, authorities say.

By Sharon Lynn Pruitt
Digital Original
How To Use DNA To Crack A Case

More than 30 years after 18-year-old Traci Hammerberg was found dead in a snowy driveway, authorities in Wisconsin say they have finally tracked down her killer, thanks to forensic genealogy. 

Hammerberg’s partially undressed body was discovered in the driveway of a Grafton home in the early morning hours on Dec. 15, 1984, the Ozaukee County Sheriff's Office said during a press conference Tuesday. The teen, who lived in Saukville, was believed to have been raped and killed after leaving a party with friends at around 12:30 a.m. and embarking alone on a nearly four-mile walk home, according to authorities. 

Despite the blood and semen found on the scene, which authorities were able to use to build a DNA profile of the person who killed her, the murderer was never identified — until now.

Philip Cross, who died of a drug overdose in Milwaukee in 2012, is believed to have raped, strangled, and beat Hammerberg to death with a metallic object that night in 1984, when he was 21 years old, authorities revealed.

Traci Hammerberg Pd

The Ozaukee County Sheriff's Office spent decades investigating the crime with assistance from the state Department of Justice Division of Criminal Investigation and the FBI Behavioral Analysis Unit, but investigators turned a corner in the case in March 2019 when they decided to focus on forensic genealogy and sent their DNA evidence to the Los Angeles FBI Forensic Genetic Genealogy Team, the office said.

A private lab was able to build another DNA profile of Hammerberg’s killer, and investigators used a genetic genealogy database to identify a relative of the unidentified killer, a second cousin, which then led authorities to identify Cross as a suspect in August 2019.

His DNA, which was collected and kept on file by the local medical examiner’s office following his overdose, was then reportedly found to be a match with the semen and other evidence in the Hammerberg case.

“After almost 35 years, we have found the person that had brutally raped, strangled, and bludgeoned Traci Hammerberg to death,” Ozaukee County Sheriff James Johnson told reporters on Tuesday.

Cross, who had a criminal record filled with violence but was not known as a suspect at the time of Hammerberg’s death, had been working a late shift at Rexnord Plastics in Grafton around the time the teen went missing. Investigators theorized that he offered Hammerberg, who often accepted rides from strangers, a lift home that night. Cross was known to have an anger problem and likely would have responded with violence if the teen spurned his advances, Johnson claimed.

In a Facebook post Tuesday, the sheriff’s office confirmed that Hammerberg’s killer had finally been identified, writing, “It's true. Nearly 35 years later, we have identified Traci Hammerberg's killer through genetic genealogy DNA matching. #RestInPeaceTraci.”

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