Investigators have gotten a big break in the 1984 rape and murder of an 18-year-old Wisconsin woman, having identified a suspect using open-source DNA databases, authorities said Tuesday.

Traci Hammerberg was found raped and beaten to death in Saukville on the morning of Dec. 15, 1984, the Journal Sentinel reported.

Investigators pursued the case for decades but never solved the case. Ozaukee County Sheriff Jim Johnson called it “the largest amount of DNA tests of any case in the state of Wisconsin.”

Investigators combined DNA evidence on Hammerberg’s body with public DNA databases to identify the killer’s second cousin, Fox 6 reported. By using a family tree they were able to identify the man they contend killed Hammerberg: Philip J. Cross.

Johnson said Cross’ name had never come up in a list of suspects and he was not one of Hammerberg’s friends or associates.

BURNED REMAINS FOUND IN ILLINOIS IDENTIFIED AS WOMAN MISSING SINCE 2010

The night Hammerberg was killed, she had been at a party in Port Washington, a few miles from her home. Neil McGrath, special agent for the Wisconsin Department of Justice, said it’s likely Hammerberg got into someone’s car – either on her own or by force – during her walk home.

On his way home from a factory in Grafton, Cross and Hammerberg crossed paths, authorities say. But investigators will never know exactly what transpired: Cross died of a drug overdose in 2012.

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