A Wingstop cup tossed in the trash gave California investigators the DNA break they needed to charge a 73-year-old man with a murder that went unsolved for more than four decades.
The Contra Costa County District Attorney's Office announced the arrest of Robert Earl Gilliam in connection with the 1985 killing of 27-year-old Cynthia Alonzo, whose body was found strangled and sexually assaulted in a field in unincorporated Contra Costa County. USA Today reported that Gilliam was arrested on May 29, 2025, and faces charges of murder and sexual assault. He has not been convicted and is presumed innocent.
For Alonzo's family, the arrest caps a 40-year wait for answers. For law enforcement, it represents the latest cold case cracked by forensic genetic genealogy, a technique that has transformed how investigators approach decades-old violent crimes with preserved biological evidence.
On October 6, 1985, a passerby discovered Alonzo's body in a field near the city of Antioch. She had been strangled. A sexual assault kit was collected during the autopsy, and investigators preserved the biological evidence. But the case went nowhere. No suspect was identified, and the investigation stalled.
Alonzo was 27 years old at the time. She left behind family members who would spend the next four decades without answers about who killed her or why.
The Contra Costa County Sheriff's Office kept the case file open, and the preserved evidence would eventually prove critical. But for years, the DNA sat in storage with no matching profile in law enforcement databases.
The break came when the Contra Costa County District Attorney's cold case unit partnered with Bode Technology, a forensic laboratory, and Innovative Forensic Solutions to apply genetic genealogy techniques to the preserved evidence. Genetic genealogy works by uploading a DNA profile to public genealogy databases, identifying distant relatives of the unknown contributor, and then building family trees to narrow the pool of possible suspects.
In this case, the genealogical research led investigators to Gilliam, who was living in Antioch. The technique has solved a growing number of decades-old violent crimes since it first gained national attention with the arrest of the Golden State Killer in 2018.
Once investigators had a suspect, they needed a direct DNA sample to confirm the match. That is where the Wingstop cup entered the picture.
Investigators conducted surveillance on Gilliam and recovered a cup he had discarded at a Wingstop restaurant. The DNA on the cup matched the biological evidence collected from Alonzo's sexual assault kit in 1985. Contra Costa County Senior Deputy District Attorney Mary Knox confirmed the match in public statements about the case.
Knox stated that the DNA from the discarded cup was consistent with the 40-year-old evidence. The technique of collecting "abandoned DNA" from items a suspect throws away in public is a well-established law enforcement practice. Because the item was discarded voluntarily, investigators do not need a warrant to collect it.
Gilliam was arrested at his Antioch residence on May 29. He was booked into the Contra Costa County jail and charged with murder and sexual assault.
Gilliam, now 73, had been living in the same general area where Alonzo's body was found four decades earlier. Prosecutors have not publicly disclosed whether Gilliam had any prior criminal record or any previous connection to the victim. Investigators have not said whether they believe Gilliam knew Alonzo or whether the attack was random.
Cold case investigators often note that suspects in genealogy-solved cases have sometimes lived quietly in the same community for decades, undetected by traditional investigative methods. Gilliam's proximity to the original crime scene across 40 years raises questions that prosecutors will likely explore at trial.
The growing power of forensic genealogy has raised hopes for families in other long-stalled cases. Experts have noted that DNA and genetic genealogy could break open unresolved cases where biological evidence was properly preserved, even when traditional leads dried up long ago.
Alonzo's family released a statement through the District Attorney's Office after the arrest was announced. They expressed gratitude to the investigators and forensic teams who kept working the case.
Knox, the senior deputy DA, described the moment of notifying the family. She said the family had never given up hope that someone would be held accountable for Alonzo's death. Knox called the arrest a testament to the persistence of the cold case unit and the advances in forensic science that made the identification possible.
Authorities have not publicly confirmed whether additional charges could follow or whether investigators are examining Gilliam in connection with any other unsolved cases. That kind of review is standard when genetic genealogy identifies a suspect in a violent crime.
The Alonzo case is part of a broader wave of cold case resolutions driven by forensic genetic genealogy. Since the method's breakthrough in the Golden State Killer case, law enforcement agencies across the country have used it to identify suspects in homicides, sexual assaults, and unidentified remains cases stretching back decades.
The technique relies on the willingness of private citizens to upload their DNA to public genealogy databases. Privacy advocates have raised concerns about the expanding use of genetic data by law enforcement, but courts have generally upheld the practice when investigators follow established protocols. The collection of abandoned DNA, like the Wingstop cup in this case, sidesteps Fourth Amendment issues entirely because the suspect voluntarily discarded the item.
The role of DNA evidence in violent crime cases continues to expand, both in solving old cases and complicating newer ones where unexpected genetic profiles surface during investigation.
For prosecutors, the challenge now shifts to the courtroom. A 40-year-old case presents inherent difficulties: witnesses may have died or lost their memories, physical evidence beyond the DNA may have degraded, and the passage of time can complicate efforts to reconstruct the circumstances of the crime. But DNA evidence has proven persuasive to juries, and prosecutors in genealogy-solved cases have secured convictions even when other evidence is thin.
Gilliam is being held in the Contra Costa County jail. Prosecutors have not announced a bail amount or a date for his first court appearance. He has the right to an attorney and the presumption of innocence.
The case will test whether the DNA match alone, combined with whatever circumstantial evidence prosecutors can assemble from a 40-year-old investigation, is enough to secure a conviction. Defense attorneys in genealogy cases have sometimes challenged the reliability of degraded samples or the methodology of the genealogical research, though such challenges have rarely succeeded when the direct DNA confirmation matches.
Other cold cases across the country remain in various stages of similar forensic review. Advocates for victims' families have pushed for increased funding for cold case units and forensic testing backlogs. Some cases have been cracked through unconventional means, including true-crime investigations that generated new leads decades after the original crimes.
In high-profile cases, defense teams have also argued that untested DNA evidence could change the outcome of convictions, underscoring how central genetic evidence has become to the American justice system on both sides of the courtroom.
Cynthia Alonzo was 27 when she was killed. The man now charged with her murder is 73. The distance between those two facts tells you everything about what forensic science can recover and what it cannot. A Wingstop cup closed the evidentiary gap. Nothing closes the other one.
