Naman Shrestha
In the episode titled ‘Secrets in Pleasant Prairie’ of NBC’s ‘Dateline,’ the focus is on the mysterious and tragic death of Julie Jensen, who was found dead in her Pleasant Prairie, Wisconsin, residence in December 1998. Although the initial inspection led the authorities to believe that it was a case of suicide, further digging into her husband, Mark Jensen, revealed that he had a massive hand in her demise. As multiple pieces of evidence against him piled up, including a letter written by Julie, Mark was punished for his crimes.
Mark Jensen Poisoned His Wife Before Suffocating Her to Death
Born in 1959, Mark D. Jensen was a student at a local college in Oshkosh, Wisconsin, when he crossed paths with Julie Griffin, a Sears department store employee at the time, in 1981. Forming a romantic connection, the two began dating and moved to the village of Pleasant Prairie to mark a new beginning in their lives. Residing in the Carol Beach neighborhood, the couple got married and welcomed two sons, David and Douglas. Things became complicated between them when Julie became involved in an affair with a co-worker named Perry Tarica in the early 1990s. Later, he served as a branch manager of a St. Louis-based financial firm in Racine, Wisconsin. In the years leading up to Julie’s tragic demise, she was subjected to stalking, hang-up phone calls, and multiple pornographic photos.
It all came to a sudden halt when she was poisoned by antifreeze by 63-year-old Mark himself. Pretending not to know anything about it, he called 911 on December 3, 1998, and informed the authorities that he had found his 40-year-old wife dead in bed at their residence. He claimed that she had been sick for a few days, but it didn’t seem that serious until that morning, as she wasn’t even able to get out of bed. The autopsy reports were inconclusive, suggesting that she died of natural causes. However, there were a few suspicious circumstances surrounding her death, all pointing to the killer — Mark Jensen. He reportedly suffocated her to death in their bed when she continued breathing after the ingestion of the antifreeze, making her position on the bed seem unnatural and odd to the detectives.
Detectives Gathered a Mountain of Evidence Against Mark Jensen
The investigators also found more reasons to suspect Mark after seizing the family’s computer and finding evidence that he had searched for ethylene glycol poisoning on the morning of Julie’s death and deleted the searches. It was also learned that he was the one sending her emails with pornographic attachments from a fake email address and harassing his wife for several years. Another piece of evidence that made Mark suspicious in the eyes of the investigators was a letter written by Julie, in which he predicted her own death. She reportedly suspected her husband to be responsible for her deteriorating mental health after finding some suspicious items in his planner. A few days before her demise, she placed the letter she wrote and other items inside an envelope and handed it over to a neighbor.
In the letter, she had written, “If anything happens to me, he would be my first suspect,” mentioning how Mark had not forgiven her for the affair even after so many years. She added, “I would never take my life because of my kids — they are everything to me!” When the authorities got their hands on the letter, they confronted the suspect in April 1999. He claimed that she was not in the right state of mind when she wrote it. Soon after Julie’s death, Mark Jensen got into a relationship with Kelly LaBonte Grieman, a co-worker with whom he had been having an affair even during his marriage. A few years later, the two even tied the knot. Once the authorities had enough evidence against him, he was arrested and charged with first-degree intentional homicide on March 19, 2002.
Mark Jensen is Currently Incarcerated at a Wisconsin Prison Facility
In early 2008, Mark Jensen stood trial for his involvement in the murder of his wife and the mother of his two children, Julie Jensen. During the trial, the prosecution presented evidence in front of the jury to prove that the defendant had poisoned the 40-year-old mother with ethylene glycol (antifreeze) and suffocated her to death on the fateful morning of December 3, 1998. They also emphasized how he had discussed the same with his co-workers and a jailhouse associate during his time in custody. The prosecution also claimed that Mark had remained bitter about Julie’s affair with Perry. Even the letter she had written was used as key evidence in court.
Meanwhile, the defense argued that Julie had taken her life and tried to frame her husband. On February 22, 2008, the jury returned with a final verdict after over 30 hours of deliberations and convicted him of first-degree intentional homicide. Throughout the trial, he was supported by his two sons, who even requested to grant him a parole date. However, a few days later, on February 27, he was sentenced to life in prison without the possibility of parole. To the disappointment of the prosecution, his conviction was overturned on December 19, 2013, and he was granted release from prison in a few months’ time.
Thanks to multiple appeals from the prosecution and after several years of delay, the court agreed to a retrial, which commenced on January 9, 2023. This time around, the prosecution focused on the evidence that proved Mark was behind Julie’s harassment and the one who made searches about the antifreeze poisoning. They even called a computer analyst to back up their claims in front of the jury. Ultimately, on February 1, 2023, the killer was once again found guilty, before being sentenced to life in prison without the possibility of parole on April 14 of the same year. As of today, he is serving his time at Oshkosh Correctional Institution in Oshkosh, Wisconsin.
Read More: Kelly LaBonte: Where is Mark Jensen’s Ex-Mistress Now?
