Acclaimed true-crime series Dateline NBC unpacks Julie Jensen‘s antifreeze murder from December 1998. The episode, titled “Secrets in Pleasant Prairie,” will air on the network this Thursday, October 12, 2023, at 10 p.m. ET.
Julie, 40, was found dead in the garage of the Pleasant Prairie home she shared with her husband, Mark Jensen. Toxicology reports later determined that she had died of ethylene glycol – found in antifreeze – poisoning. Prior to her tragic demise, the mother-of-two had given a neighbor a harrowing letter, implicating her husband.
Mark’s murder conviction came a decade later in 2008, with the letter serving as key evidence. However, an appellate court vacated the same in 2011, claiming that the piece of evidence was inadmissible for the trial. Two years later, a jury once again found him guilty of the crime.
Julie Jensen’s letter and the Antifreeze murder case, explored
According to People Magazine, on November 21, 1998, Julie gave a letter to her neighbors. Addressed to the Prairie Police Department, she expressed concern pertaining to her safety and implicated her husband in it. Nearly two weeks later, Mark found the mother-of-two dead in their garage.
In the letter, the 40-year-old reportedly wrote that “if anything happens to me, he [Mark] would be my first suspect. She disclosed crucial details about their relationship and how it “deteriorated to the polite superficial”.
The victim further wrote, “I know he’s never forgiven me for the brief affair I had with the creep seven years ago. Anyway, I do not smoke or drink…Mark wants me to drink more with him in the evenings. I don’t. I would never take my life because of my kids—they are everything to me! I pray I am wrong and nothing happens…but I’m suspicious of Mark’s suspicious behavior and fear for my early demise.”
ABC News stated that investigators learned about the letter a day after Julie Jensen’s death from Ted and Margaret Wojt. She had asked them to hand the letter to the police “if anything happens”. The Wojts handed police a sealed envelope, comprising the letter and the photo of a shopping list that included a syringe and chemicals.
The same ABC report cited other significant evidence, including Mark Jensen’s affair with a co-worker at his brokerage firm before his wife’s death. He later married the woman. The accused’s former co-worker, Ed Klug, testified that in the fall of 1998, he openly spoke about harboring hate towards Julie. Furthermore, he also mentioned poisons and websites for murdering a spouse.
Prosecutors alleged that Mark slowly and intentionally poisoned the 40-year-old with antifreeze and sleeping pills before suffocating her to death with a pillow. They proved his guilt using evidence apart from the letter, including internet searches and his suspicious behavior.
A jury first convicted the accused of murder in 2008, which was then vacated in 2011. He once again stood trial in early 2023. A second jury found him guilty of first-degree intentional homicide on February 1. He received life in prison.
