Florida teen girl's remains found at serial killer's home identified 42 years after she vanished

Billly Mansfield Jr. was convicted of sexually assaulting and murdering five women with the help of his younger brother and father

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The remains found at a Florida serial killer's home more than four decades ago have been identified as missing teen Theresa Caroline Fillingim, local authorities said.

Seventeen-year-old Fillingim vanished in 1980 in Tampa, Florida, and her sister Margaret Johns, who reported her disappearance, finally has closure after 42 years.

"It gives me peace because I know I didn't lose her, that she was taken," Johns told WFLA. "The sad part of it is my whole family never knew what happened to her. My dad died without knowing, my mom died without knowing."

A year after Fillingim vanished, authorities found four sets of human remains at the 6-acre family home of Billy Mansfield Jr., which was dubbed by neighbors as the "House of Horrors," according to Tampa Bay Times.

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A photo combination of Theresa Carolina Fillingim and Florida serial killer Billy Mansfield Jr. Fillingim's remains were found on his family's property in 1981 - but not identified as the missing teen until 2022.

A photo combination of Theresa Carolina Fillingim and Florida serial killer Billy Mansfield Jr. Fillingim's remains were found on his family's property in 1981 - but not identified as the missing teen until 2022. (Hernando County Sheriff's Office/ California Department of Corrections)

Two of the victims were immediately identified, but the other two were not.

Thanks to advances in DNA technology and a partnership with the University of North Texas and Parabon Nano Labs, one of the sets of remains excavated from Mansfield's property was finally identified as Fillingim's.

Samples of her remains were sent to various labs over the years, but a DNA profile was not developed until 2020, the Hernando County Sheriff's Office announced in a press release last week.

The profile was entered into the national database but did not hit a match.

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Researchers tried again using Parabon's new "Snapshot DNA Phenotyping" services to produce trait predictions for the victim, the sheriff's office said.

The new profile was used to create their own "actionable leads," and a DNA sample taken from Fillingim's sister confirmed the missing teen's identity, according to the release.

Mansfield was convicted of murdering five women between 1975 and 1980 and sentenced to life in prison, which he is serving in California. 

The remains of Theresa Caroline Fillingim, found on a Florida serial killer's property, were finally identified in 2022.

The remains of Theresa Caroline Fillingim, found on a Florida serial killer's property, were finally identified in 2022. (Hernando County Sheriff's Office)

After Mansfield was arrested for raping and fatally strangling 30-year-old Rene Sailing at a tavern in California in 1980, an anonymous tipster called Hernando authorities and told them to search the family property, which doubled as a junkyard.

Investigators uncovered the remains of 15-year-old Elaine Zeigler, a tourist from Ohio who vanished from a nearby campground, 21-year-old Sandra Graham, who went missing in 1980, and Fillingham. The fourth woman still has not been identified.

All four women were sexually assaulted by Mansfield, his younger brother Gary, and their father, William Mansfield Sr., the Tampa Bay Times reported, citing court records.

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It was Mansfield, though, who ultimately killed the women and often dismembered them, according to the newspaper.