In August 1988, 18-year-old Tracy Whitney was last seen leaving a Burger King after an argument with her ex-boyfriend. Less than a day later, fishermen discovered her body in a river near Sumner, Washington, about 12 miles from Tacoma. An autopsy revealed Tracy had been sexually assaulted and strangled, with her death ruled as a homicide.

Detectives collected DNA samples from her body, likely belonging to the killer, and conducted interviews and polygraph tests. Despite their efforts, no suspects were identified, and the case went cold.

For Robin Whitney, Tracy’s younger sister, the loss was devastating. Only 11 years old at the time, Robin avoided discussing her sister for decades, unable to process the trauma. “I didn’t want to think about what happened to her or how scared she must’ve been,” she shared. Over time, grief and frustration about the unsolved case weighed heavily on her.

A breakthrough came roughly 10 years ago when Robin learned that DNA from the crime scene had been preserved. The revelation brought her a sliver of hope. She began sharing memories of Tracy with her own daughters, something she hadn’t been able to do before. Her father, who had regularly visited the sheriff’s office over the years, also renewed his faith in the investigation.

In 2005, the DNA sample was uploaded to the FBI’s national database, but no matches were found. However, advancements in forensic science reignited the case in 2022. With a grant from the state attorney general’s office, the Pierce County Sheriff’s Office sent the DNA to Parabon NanoLabs for genetic genealogy testing. This method combines DNA analysis with family tree research and has become a powerful tool for solving cold cases, such as the infamous Golden State Killer case.

The lab traced the suspect’s family line back to the 1700s, ultimately identifying John Guillot Jr. as the likely perpetrator. Tragically, Guillot Jr. had died just eight months before this discovery. To confirm his identity, investigators used DNA from his deceased son, John Guillot III, whose genetic profile matched the sample from the crime scene.

Detectives believe Guillot Jr. and Tracy were strangers before the crime, and because Guillot Jr. was cremated, his DNA couldn’t be uploaded to the FBI database to connect him to other possible crimes.

For Robin, the revelation brought a mixture of emotions. “I’ve waited my entire life to know who did this,” she said. While she feels some justice knowing her sister’s case is solved, she is saddened that Guillot Jr. avoided facing the criminal justice system.

The resolution has brought Robin an emotional release she didn’t realize she needed. “Since learning the truth, 36 years of locked-up emotions have come out,” she said. “I grieved her as a child, and now I’m grieving her as an adult. It’s painful, but it’s also a relief.”

The community’s support has also been a source of comfort. “The attention Tracy is getting now feels like a form of justice,” Robin reflected. “People remember her, they miss her, and that means the world to me.”