Title: The Antifreeze Murders: How a Mother-Daughter Duo Methodically Killed Their Own Family
By June 2013, the Staudte family of Springfield, Missouri, seemed plagued by an unrelenting curse. First, 61-year-old Mark Staudte, the patriarch, was found dead in April 2012. Just months later, on September 2, his 26-year-old autistic son, Shaun, also perished. Then, in June 2013, their daughter, Sarah, was hospitalized in critical condition. What appeared to be a tragic string of misfortunes was, in reality, a meticulously planned and cold-blooded killing spree orchestrated by none other than Mark’s wife, Diane Staudte, with the help of her favorite child, Rachel.
A Trail of Unnoticed Murders
Mark’s death seemed natural. Diane told authorities he had been feeling unwell for days but had refused medical attention. Given Mark’s unhealthy lifestyle, officials saw no reason to question the cause of death.
With the insurance payout, Diane upgraded her life—moving to a nicer home in Springfield. But death followed. On September 2, Diane discovered Shaun lifeless on his bedroom floor. She attributed his death to seizures and flu-like symptoms.
An anonymous tip suggested Diane was responsible for Shaun’s death, but an autopsy failed to uncover any foul play. Testing for ethylene glycol, the lethal component in antifreeze, isn’t standard procedure unless foul play is suspected. And with symptoms that mimic natural illnesses—nausea, vomiting, slurred speech—Diane’s deadly scheme remained undetected.
Shaun was buried without a funeral. His mother didn’t bother with a service.
A Mysterious Illness Sparks Suspicion
By June 2013, 24-year-old Sarah Staudte was fighting for her life in a hospital bed. Doctors were baffled by her symptoms—organ failure, internal bleeding, and a brain hemorrhage—but had no answers.
Then came a call that changed everything. On June 11, 2013, an anonymous tipster—later revealed to be the family’s pastor—told authorities that Diane was responsible for “two or three homicides.” He pointed to Mark, Shaun, and Sarah as her victims.
When investigators visited Sarah’s hospital room, they learned that while her daughter was at death’s door, Diane was more interested in planning a vacation. Suspicious, police pressed further. One doctor suggested that Sarah may have been poisoned.
On June 20, 2013, Diane sat across from investigators in an interrogation room. She denied involvement—until she didn’t. Eventually, she confessed. The murders were chillingly methodical. She had laced Mark’s sports drinks with antifreeze. She had poured it into sodas for Shaun and Sarah. The motive?
“I hated his guts,” Diane said of Mark.
She dismissed Shaun’s life as an inconvenience, calling him “more than a pest.” And Sarah? She was unemployed and had student loan debt—dead weight, in Diane’s eyes.
The Unthinkable: A Daughter’s Betrayal
Diane didn’t act alone. Police uncovered a journal belonging to Rachel, her 22-year-old daughter. One chilling entry, dated June 13, 2011, read:
“It’s sad when I realized how my father will pass on in the next two months… Shaun, my brother will move on shortly after… It will be tough getting used to the changes, but everything will work out.”
When Rachel was confronted with her writings, she finally broke. She admitted she had helped plan the murders. Diane had pitched the idea, and they had debated the specifics. Rachel had objections—she argued against killing her siblings—but ultimately, she participated.
“Mom brought it up, and then we discussed,” Rachel admitted.
Shaun, she said, could have been placed in assisted living, but Diane refused. Sarah was also deemed “unneeded.” Even worse, Rachel revealed that their ultimate plan was to kill their youngest sibling, then just 11 years old.
Diane and Rachel only took Sarah to the hospital because Rachel didn’t want another death in the house.
Justice Served—but Too Late
Sarah survived but suffered permanent neurological damage. She now resides in an assisted-living facility, while her youngest sister was placed in foster care.
Rachel took a plea deal in 2015, admitting guilt to two counts of second-degree murder and one count of first-degree assault. She was sentenced to two life terms with eligibility for parole after 42.5 years. At her sentencing, she turned to Sarah and said, “I’m sorry I couldn’t find the courage to stand up for what was right.”
Diane, meanwhile, pleaded guilty to two counts of first-degree murder and one count of assault. She received three life sentences without the possibility of parole.
Yet, in a shocking 2022 interview, she tried to change the story, suggesting that her husband had “dangerous people” in his life and that “somebody probably came in and gave him something.” But the facts were clear—Diane had confessed in vivid detail.
A Crime That Defied the Odds
Forensic psychologist Dr. Rod Hoevet weighed in on the bizarre nature of the case.
“Women don’t engage in a lot of violent crime as a general rule,” Hoevet explained. “That a mother would be committing a crime against her own family is already pretty unusual… Then the idea that she would bring her daughter into it to kill her own family members—and apparently convinced her of it—is so unusual.”
The Staudte case defied logic and shattered the stereotype of maternal love. A mother and daughter, bound not by affection but by an insidious plan, turned their home into a house of horrors—until justice finally caught up with them.
