Mark Jensen of Wisconsin: Trial, Retrial, and Life Sentence

Mark Jensen is a Wisconsin man twice convicted of murdering his wife, Julie, at their Pleasant Prairie home in December 1998 by poisoning her with ethylene glycol and then suffocating her. His first conviction in 2008 was overturned on federal habeas review because a handwritten letter Julie left with neighbors — naming him as her likely killer if anything happened to her — should not have been admitted under the Sixth Amendment’s Confrontation Clause. A second Kenosha County jury convicted him in 2023 without the letter, and he was again sentenced to life in prison without the possibility of parole.

Julie Jensen’s Death in Pleasant Prairie

On December 3, 1998, Julie Jensen, 40, was found dead in bed at the family’s home in Pleasant Prairie, a village in Kenosha County. Mark Jensen, then in his late thirties, told investigators he discovered her body. Toxicology later confirmed ethylene glycol — the toxic ingredient in antifreeze — in her system, though at such small amounts that it took months for investigators to identify the substance.¹ Dr. Stacey Hail, a medical toxicologist who later testified, said calcium crystals in Julie’s kidneys were consistent with ethylene glycol poisoning and that the low blood levels suggested she was in a late stage of the poisoning process.²

The medical examiner ruled the death a homicide caused by two factors: ethylene glycol poisoning and asphyxiation. Prosecutors theorized that Jensen tried to kill Julie with poison and, when she did not die quickly enough, smothered her by pushing her face into a pillow.¹

The Letter Julie Left With Her Neighbors

In late November 1998, days before her death, Julie gave a sealed envelope to her neighbors, Ted and Margaret Wojt, with instructions to hand it to police if anything happened to her. The day after Julie died, they did.³

Inside were a handwritten letter and a photograph of a shopping list that included a syringe and chemicals. Julie wrote that she was “suspicious of Mark’s suspicious behaviors” and feared her “early demise.” She stated plainly: “If anything happens to me, he would be my first suspect.” She said she would never take her own life because of her children — “They are everything to me” — and wrote that her husband had “never forgiven me” for a brief affair years earlier.³ She had also left two voicemails for a local police officer expressing similar fears and identifying her husband as a suspect.⁴

The letter became the most contested piece of evidence in the case, and later jurors described it as a road map to the murder.

What Else Investigators Found

Investigators built a circumstantial case over the next several years. On the family’s desktop computer, someone had searched on the morning of Julie’s death for “diminished consciousness from ethylene glycol poisoning” and then deleted the search records. A forensic analyst later recovered additional searches for “botulism,” “poisoning,” and “ethylene glycol” and testified that the user had “tried to cover up what they were searching for.” Internet history had been deleted on November 29, December 2, and December 3, 1998 — the last date being the day Julie was found dead.⁵

Ed Klug, a former coworker at a brokerage firm, told investigators that roughly a month before Julie’s death he and Jensen were drinking after a work conference in St. Louis when Jensen spoke about hating his wife and described ways to poison a spouse, specifically naming ethylene glycol, Benadryl, and pool chemicals. Klug testified that Jensen described substances “that would crystallize inside a body and go undetected.”⁶⁷ Klug said he did not initially report the conversation because he feared Jensen would retaliate against him and his family.

Witnesses said Jensen showed no visible grief, was observed laughing and joking at Julie’s wake, and shortly after the funeral disposed of her belongings in garbage bags. He had also been carrying on an affair with a coworker, Kelly Brooks, in the months before Julie died, and asked a friend whether it would be appropriate to bring Brooks to the wake.⁶⁸ Brooks later divorced her husband and married Jensen.⁹

On March 19, 2002, more than three years after Julie’s death, Mark Jensen was charged with first-degree intentional homicide.¹

The 2008 Trial and First Conviction

Before trial, the admissibility of Julie’s letter went up to the Wisconsin Supreme Court. In its 2007 decision (Jensen I), the court held that the letter and voicemails were “testimonial hearsay” under the Confrontation Clause. Ordinarily that would have kept them out. But the court also adopted a broad version of the “forfeiture by wrongdoing” doctrine: if the prosecution could prove by a preponderance of the evidence that Jensen had caused Julie’s unavailability by killing her, he would forfeit his right to confront her. After a ten-day hearing, the trial court found he had killed her and let the letter in.¹⁰

At the 2008 trial, prosecutors made Julie’s letter the centerpiece, alongside the computer search evidence, Klug’s testimony, and testimony from a jailhouse informant, Aaron Dillard. Dillard, who had been housed on the same cell block as Jensen for about two and a half days, claimed Jensen confessed to poisoning Julie with antifreeze-laced juice and then smothering her with a pillow when the poison worked too slowly. Dillard admitted on the stand to at least eight convictions for fraud and theft and said he had “been a liar and a con man,” acknowledging his cooperation was partly motivated by a plea deal. “At that point I decided it was a way out,” he said.¹¹

The defense argued Julie had been depressed and taken her own life, framing her husband in the process. Defense experts disputed the suffocation theory, and a poison specialist argued Julie could have ingested the ethylene glycol herself.¹²

After 32 hours of deliberation, the jury convicted Jensen of first-degree intentional homicide. Jurors later called Julie’s letter a “road map” to the murder and said it was the turning point in their deliberations.¹³ They also said they could not reach a definitive conclusion on whether Julie had been suffocated, basing the conviction primarily on the poisoning evidence.¹² He was sentenced to life in prison without parole.

Why the Conviction Was Overturned

Shortly after Jensen’s trial, the U.S. Supreme Court decided Giles v. California (2008), which narrowed the forfeiture-by-wrongdoing doctrine. Under Giles, the exception applies only when the defendant acted with the specific intent to prevent the witness from testifying. The prosecution’s theory here was that Jensen killed Julie to be with his mistress, not to silence her as a witness, so the broader Wisconsin standard no longer held.¹⁰

The Wisconsin Court of Appeals in 2011 (Jensen II) acknowledged that admitting the letter was likely erroneous under Giles but called the error “harmless beyond a reasonable doubt.”¹⁴ Jensen then filed for federal habeas corpus. In December 2013, U.S. District Judge William Griesbach vacated the conviction, finding the state court’s harmless-error analysis flawed.¹ In 2015, the Seventh Circuit affirmed in Jensen v. Clements, finding the letter had a “substantial and injurious effect” on the verdict, that no other piece of evidence matched its emotional and dramatic impact, that it was the “essential component of the State’s case,” and that it had been the last exhibit left with the jury before deliberations.¹⁰

Back in state court, Kenosha County Circuit Court Judge Chad Kerkman tried in 2017 to reinstate the conviction by finding the letter admissible, but the Wisconsin Court of Appeals reversed him. The Wisconsin Supreme Court then took up the matter and, in March 2021 (Jensen III), ruled definitively: the 2007 finding that Julie’s statements were testimonial remained the law of the case, later U.S. Supreme Court decisions in Michigan v. Bryant and Ohio v. Clark had not altered that analysis, and the letter and voicemails must stay out at any new trial.⁴ The court ordered a new trial.

The 2023 Retrial Without the Letter

Jensen’s second trial began on January 9, 2023, in Kenosha County before Judge Anthony Milisauskas. Prosecutors had to build the case without the letter or the voicemails.¹⁵

They leaned on evidence that had been secondary in 2008 and introduced material that was new. The computer forensic evidence returned, including the deleted searches for ethylene glycol poisoning. Klug again testified about Jensen’s discussion of poisoning methods. Dillard reprised his account of the jailhouse confession — this time, according to prosecutors, without a plea deal in place.¹⁶

The most significant new evidence involved a campaign of harassment Julie had documented before her death. Prosecutors showed that an external computer drive contained a fake email loaded with pornographic attachments that Mark Jensen had sent to himself but altered to look as though it came from someone else. He then presented the email to Julie as proof that an unknown person was tormenting her, when he was the source. Deputy District Attorney Carli McNeill said the evidence was uncovered with the help of a Department of Justice computer analyst.¹

After 15 days of testimony and less than one full day of deliberations, the jury found Mark Jensen guilty of first-degree intentional homicide on February 1, 2023.¹⁵

Sentencing and Current Status

On April 14, 2023, Judge Milisauskas sentenced Jensen to life in prison without the possibility of parole, the same sentence he received after his first conviction.¹⁷

Jensen had asked for parole eligibility, telling the court: “Please grant parole eligibility so the family and I can move forward and heal.” He said his three sons had suffered because of the case and “deserve my help, if they want it.”¹⁸¹⁷

Three of Julie’s brothers — Michael, Larry, and Paul Griffin — addressed the court. Larry called Jensen’s actions “cruel and inhuman” and “unforgivable.” Paul told the judge he had written a similar statement 15 years earlier and that “nothing has changed in that time,” asking the court to “show no mercy for Mark Jensen. Why you might ask? Because he showed no mercy to his wife, my sister, Julie Jensen.” McNeill told the court Jensen “should not breathe the free air outside of a prison cell.”¹⁸

Jensen has maintained his innocence and stated his intention to appeal the second conviction. No decision on any such appeal has been published in the available reporting.¹⁹²⁰

1
NBC News. Mark Jensen Julie Poisoning Death Conviction
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Courthouse News. Wisconsin Man Again Found Guilty of Killing Wife With Antifreeze at Retrial
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Courthouse News. Wisconsin Antifreeze Murderer Again Sentenced to Life Without Parole