'Secrets in Pleasant Prairie': NBC's Dateline to highlight Julie Jensen antifreeze murder

In February 2023, a jury, for the second time, found Mark Jensen guilty of killing his wife, Julie Jensen, at their Pleasant Prairie home in 1998.
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Posted at 12:25 PM, Oct 11, 2023
and last updated 2023-10-11 13:25:24-04

Dateline NBC will debut its season premiere this Friday by highlighting the 1998 murder of Julie Jensen in Pleasant Prairie.

The case centers around a former stockbroker, Mark Jensen, poisoning his wife so that he could be with his mistress.

Mark Jensen
Mark Jensen after the jury's verdict was read in court on Wednesday.

In February 2023, a jury, for the second time, found Mark guilty of killing his wife, Julie, at their home. It was Mark's second conviction of first-degree intentional homicide. In 2008, a jury convicted him and he was sentenced to life without parole. In 2021, his sentence was vacated after the Wisconsin Supreme Court ruled evidence in the first trial violated his rights.

In both trials, the state claimed Mark used antifreeze to slowly poison Julie so he could continue an affair with a woman he eventually married. According to Court TV, the case was built around a letter Julie wrote suspecting that Mark was trying to kill her, as well as statements to police, a neighbor, and her son's teacher.

The defense argued Julie was depressed and took her own life to frame her husband.

You can watch the "Secrets in Pleasant Prairie" episode on Friday at 9 p.m. on NBC 26. Check out the preview for the episode on