The Southside Strangler: How DNA Technology Took Down a Cold-Blooded Killer
In the dark corridors of criminal history, few killers have left a trail as chilling as Timothy Spencer, the Southside Strangler. His reign of terror in Virginia during the fall of 1987 had police baffled—until a groundbreaking forensic tool turned the tide and brought him to justice. This is the gripping story of how DNA evidence, a fledgling technology at the time, became the key to capturing a predator who had eluded law enforcement for far too long.
A Killer on the Prowl
Spencer hunted his victims in Richmond and Arlington, breaking into homes under the cover of night. His method was terrifyingly precise—he would sexually assault the women, bind their hands, and strangle them using belts, ropes, or socks. Then, like a ghost, he would disappear, leaving behind almost no clues.
With a city paralyzed in fear, police scrambled for answers. But despite their best efforts, they had little to go on—until one detective followed his instincts and uncovered the terrifying truth.
A Trail of Victims
The list of Spencer’s victims is heartbreaking. Among them was Susan Tucker, 44, an editor with the U.S. Forest Service, whose decomposed body was discovered in her Arlington home. Debbie Dudley Davis, 35, a magazine account manager, was found strangled in her Richmond apartment. Dr. Susan Hellams, 32, a neurosurgical resident, was brutally murdered in her own bedroom. The youngest, 15-year-old Diane Cho, an honors student, was found lifeless in her home the morning after her parents tucked her into bed.
Each of these women had their lives cut short in the one place they should have felt safest—their own homes.
The Break in the Case
At first, the connection between these murders wasn’t clear. But Arlington County Detective Joe Horgas had a gut feeling—something about these cases mirrored an earlier murder from 1984. Carolyn Hamm, a 32-year-old attorney, had been found hanged in her basement. A man named David Vasquez had been convicted for her murder, but Horgas suspected they had the wrong man.
With no clear suspects, Horgas took a chance on a revolutionary forensic tool—DNA testing. He submitted semen samples from the Tucker and Hamm crime scenes to Lifecodes, a New York-based lab, in hopes of finding a match.
At the same time, an FBI profile suggested that the killer’s gap between murders could be explained by incarceration. That led Horgas back to an old burglary suspect—Timothy Spencer. The records showed Spencer had been imprisoned in 1984 and released in September 1987, just before the new string of murders began.
DNA: The Game-Changer
Armed with a timeline, police arrested Spencer at his Richmond halfway house in January 1988. There, they found a chilling piece of evidence—an infinity symbol drawn on his mattress, similar to the one found on Diane Cho’s body.
Then came the moment that changed everything. DNA testing confirmed that the semen from multiple crime scenes belonged to Spencer. The odds of it belonging to anyone else? One in 705 million.
In July 1988, Spencer became the first serial killer in U.S. history to be convicted based on DNA evidence—a turning point in forensic science. He was later convicted in separate trials for all four murders and executed in 1994.
Meanwhile, David Vasquez, the wrongly convicted man, was exonerated and pardoned in 1989.
A Killer Unlike Any Other?
Forensic psychologist Joni Johnston, who has studied serial murderers extensively, remains perplexed by Spencer. “I’ve always believed there’s no such thing as a born serial killer,” she says. “But Spencer comes as close as I’ve seen. There’s no evidence of severe trauma in his childhood, no clear turning point that made him into the monster he became.”
Criminologist Stephen Jones agrees, noting that Spencer’s DNA was the linchpin of the case. “Without it, he might have walked free,” Jones says. “His M.O. was similar to many unsolved cases. But DNA sealed his fate.”
How One Case Changed Criminal Investigations Forever
Timothy Spencer’s case wasn’t just a victory for justice—it was a seismic shift in criminal investigations. Before his conviction, DNA testing was virtually unheard of in courtrooms. After his trial, it became one of the most powerful tools in forensic science.
“It changed the whole world of crime fighting,” says former Virginia assistant attorney general Rick Conway. “Juries no longer had to rely solely on circumstantial evidence. DNA told the story.”
And in Spencer’s case, it was a story that ended with the cold-blooded killer facing the justice he so ruthlessly denied his victims.
