The Antifreeze Murder of Pleasant Prairie
- 608areascanner
- Sep 12
- 2 min read
Updated: Sep 19
In December of 1998, the quiet town of Pleasant Prairie, Wisconsin, was shaken by a crime that seemed torn from the pages of a psychological thriller. Julie Jensen, a devoted mother and wife, was found dead in her home under circumstances that at first looked suspiciously ordinary. But behind the façade of family life, a dark plot was unraveling—a plot laced with betrayal, obsession, and antifreeze.
Julie Jensen had long harbored doubts about her husband, Mark. Their marriage appeared stable on the surface, but Julie confided in friends and family that she feared for her safety. She even went so far as to document her concerns in letters and notes. In one chilling message, Julie wrote that if anything happened to her, Mark should be considered the prime suspect.
Julie’s fears tragically came true in December 1998, when she fell gravely ill. Doctors were unable to save her, and at first, her death was a mystery. But toxicology reports revealed a deadly presence in her system: ethylene glycol, the primary chemical found in antifreeze. The poison causes a slow, agonizing decline, damaging organs until the body shuts down. Investigators suspected that Julie had not taken it voluntarily.
As detectives dug deeper, Mark Jensen’s behavior raised red flags. Not only had Julie voiced her fears about him, but investigators also uncovered evidence that he had been conducting research on poisoning methods. He was also engaged in an extramarital affair, adding a possible motive for wanting his wife out of the way.
The most haunting piece of evidence, however, came from Julie herself. Her handwritten note—essentially predicting her own murder—became a cornerstone of the prosecution’s case. Few murder cases had ever contained such direct words from the victim beyond the grave.
A Trial Years in the Making
The legal battle over Julie’s death stretched on for years, delayed by appeals and debates over whether her note should be admissible in court. In 2008, a jury finally convicted Mark Jensen of first-degree intentional homicide, sentencing him to life in prison without parole. But the story didn’t end there.
In 2021, after continued legal wrangling, his conviction was overturned on grounds that Julie’s letter might have unfairly influenced the jury. A retrial followed in 2023, where prosecutors presented forensic evidence, witness testimony, and the damning trail of Mark’s internet searches. This time, despite the long delay, the verdict remained the same: guilty.
The murder of Julie Jensen stands as one of Wisconsin’s most infamous cases—a haunting example of a victim who foresaw her own death and left behind a warning. Her case is remembered not only for its shocking details but also for the extraordinary legal battles it sparked, testing the limits of evidence and a victim’s voice from beyond the grave.
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Sources:
Associated Press
CBS News
Milwaukee Journal Sentinel
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