A vibrant and social young woman, Mary Duggan was known to her family as the “life of the party.” The 22-year-old female lived with her father in the Reseda neighborhood of Los Angeles and was a regular in the lively Southern California music scene. Her life, full of promise and energy, was brutally cut short in the summer of 1986, leaving her family with decades of questions and grief.
On the morning of June 9, 1986, Burbank police discovered Mary’s body in the trunk of her 1980 Ford Mustang. The car had been left in an empty parking lot near the intersection of Glenoaks Boulevard and Cohasset Street. An autopsy later revealed that Mary had been sexually assaulted and had died of asphyxiation. A tissue had been forced down her throat, and a knitted fabric gag was found in her mouth, with a matching piece used as a ligature to strangle her.
For years, her murder remained unsolved, a cold case that offered no suspects and no answers.
The investigation into Mary’s death stalled for more than three decades. Detectives pursued leads, but the case grew cold, one of many unsolved homicides in Los Angeles County. The break investigators needed would not come until the advent of new technology. In 2019, in what would become the first case of its kind for the Los Angeles County District Attorney's Office, detectives used investigative genetic genealogy to analyze DNA evidence recovered from the crime scene. By uploading the suspect's DNA profile to a commercial genealogy database, they found a partial match to a relative, which allowed them to build a family tree and ultimately zero in on a suspect.
This revolutionary forensic technique led them to Horace Van Vaultz Jr., a man with a history of violence against women. Investigators began surveillance on Vaultz and were able to obtain a sample of his DNA from a discarded item. The sample was a perfect match to the DNA found on Mary’s body. In November 2019, more than 33 years after Mary’s murder, the 64-year-old Van Vaultz was arrested during a traffic stop in Inglewood.
The DNA evidence also linked Van Vaultz to the 1981 murder of 21-year-old Selena Keough in Montclair, who had also been sexually assaulted and strangled. Prosecutors charged Van Vaultz with two counts of first-degree murder with the special circumstances of multiple murders, rape, and sodomy. During the trial, Deputy District Attorney Beth Silverman described Vaultz as a "sexually motivated serial killer" who derived pleasure from inflicting pain. Though Van Vaultz testified in his own defense, claiming he was a "swinger" who couldn't remember Mary or Selena, he offered no explanation for how his DNA was found on and inside their bodies.
In August 2022, a jury found Horace Van Vaultz Jr. guilty on all counts. He was subsequently sentenced to two consecutive terms of life in prison without the possibility of parole. The conviction brought a measure of justice to a family that had waited an entire generation for answers. At the sentencing, a statement from Mary's mother, Maureen, was read in court. "When you get past the shock of hearing your daughter is dead, you wonder who is out there that did this," she wrote. "Then you just miss her so much, every day, at every family gathering and holiday... It's one thing that your child dies at only 22 years old. It's a whole other thing to know she suffered in dying at the hands of a monster."
The use of genetic genealogy not only solved Mary's murder but also brought to light Van Vaultz's reign of terror. DNA evidence presented at his trial also implicated him in the 1986 murder of 25-year-old Janna Rowe in Ventura County, a crime for which he had been tried and acquitted in 1988, long before DNA testing was a standard tool. While he could not be retried for that crime, the evidence solidified his profile as a serial predator. Horace Van Vaultz Jr. is now incarcerated at California State Prison, Corcoran, where he will spend the remainder of his life.
