Killer Cases: Husband Kills Wife with Antifreeze for His Mistress

Julie Jensen was found dead in her bed by her husband, Mark, in December 1998. She had been sick for three days. The initial autopsy failed to determine a cause of death, leaving investigators with an unknown manner of death (accident, suicide, or homicide). It took years and further investigation to pinpoint the cause.

An otherwise healthy 40-year-old woman was found dead in her bed. The autopsy 'failed to determine the cause of death calling it pending.'

Days before her death, Julie gave a sealed letter to a neighbor, instructing them to give it to the police if anything happened to her. The letter expressed her fear of Mark, stated their relationship had deteriorated, and explicitly denied any intent to harm herself or abandon her children. It also contained a photograph of a post-it note in Mark's handwriting listing 'own drug supply, lirium, bag, hands, syringe,' suggesting a murder plot.

A neighbor handed law enforcement a sealed envelope from Julie, given a week and a half before her death, stating 'if anything happens to me, give this to the police.' The letter detailed fears about her husband, stated she would never harm herself or leave her sons, and included a photo of Mark's suspicious note.

Investigators seized the family computer and discovered internet searches for 'ways to kill someone,' 'botulism,' 'pipe bombs,' and specifically 'ethylene glycol poisoning.' These searches were conducted in the days leading up to Julie's death, including when she was too ill to get out of bed, strongly implicating Mark.

Internet searches on the family computer included 'ways to kill someone,' 'botulism,' 'pipe bombs,' and 'ethylene glycol poisoning.' These searches occurred 'in the two days before she died,' while Julie was 'incapable of even sitting up in bed by herself.'

Based on the computer searches, investigators requested a re-evaluation of Julie's toxicology. This led to the discovery of ethylene glycol, the primary component of antifreeze, in her blood, stomach, and urine. Ethylene glycol poisoning is a painful and ultimately fatal process that causes organ shutdown.

Ethylene glycol is 'not tested for at autopsy' unless there's a reason. A re-evaluation found 'ethylene glycol in her blood... stomach and... urine.' Ethylene glycol causes 'cardiac arrhythmia,' 'difficulty breathing,' and 'organs shut down.'

Mark Jensen was having an affair with Kelly Labonte, who moved into his home shortly after Julie's death. Testimony revealed emails between Mark and Kelly expressing love and a desire to 'clean up our lives' to be together. A friend, Edward Clug, testified that Mark discussed undetectable ways to kill his wife to avoid paying maintenance in a divorce.

Kelly Labonte moved in shortly after Julie's death. Emails from Kelly to Mark stated 'I do love you even more now.' Edward Clug testified Mark discussed 'ways to kill your wife that are undetectable at autopsy' to avoid 'pay maintenance.'

Aaron Dillard, an inmate with Mark Jensen, testified that Mark confessed to poisoning Julie's juice with ethylene glycol. Dillard also claimed Mark admitted to smothering Julie with a pillow after the poison didn't kill her quickly enough, a detail corroborated by the medical examiner's advanced theory.

Aaron Dillard, an inmate, testified Mark 'confessed that he put the ethylene glycol in Julie's juice.' Mark then 'sat on her back and then pressed her face into the pillow' when she wasn't dying fast enough.

Mark Jensen was initially convicted in a 2008 trial, with Julie's letter being a central piece of evidence. However, a federal judge ordered a new trial, ruling the letter inadmissible due to the Confrontation Clause of the US Constitution, which grants the accused the right to confront witnesses. Despite this setback, prosecutors secured a second conviction in 2023 without the letter.

The first trial took six years due to litigation over Julie's 'letter from the grave.' The 'confrontation clause' was cited, as Mark couldn't confront a dead witness. A federal judge ordered a new trial, ruling the letter 'should not have been admitted.' Mark was found guilty again in 2023.