For people on the outside looking in, Julie Jensen appeared to have it all: a successful stockbroker husband, Mark, to whom she'd been married for 14 years, two wonderful sons and a beautiful suburban home on tony Lakeshore Drive in Pleasant Prairie, Wis. "We all looked up to her as being a perfect mother," said friend Kim Shaw.
"[Julie and Mark] would always be outside, always working on some kind of project," remembered her friend and next-door neighbor Margaret Wojt. "Just laughing and having fun with it ... it was amazing to watch them."
But gradually, their marriage started to unravel. Wojt's husband, Ted, told "20/20" Mark had wanted Julie to be more sexually experimental. "She said, 'Aw, [Mark] wants me to be like these other women ... his friends. They go to the bars, three in the morning. They go to the strip clubs ... Drinking ... I'm not that. I don't want it."
Friends say Julie had previously contemplated divorce, but Wojt said Julie told her, "Mark would kill me first, before he divorced me."
Then, on Dec. 3, 1998, 40-year-old Jensen was discovered dead in her bed by her husband Mark. In the early hours of the investigation, police said suicide was the likely cause of death. District Attorney Bob Jambois was at the Jensen house that day and felt differently.
"It didn't look right," he said.
The family quickly held funeral services.
"Mark was standing five feet from her casket laughing and joking and acting like someone at a cocktail party" said Vorwald. Neighbor Carrie Ashley said, "I would probably mourn a stranger more than he mourned Julie."
When the autopsy came in, it did not confirm Jambois' suspicions and found no evidence of foul play. Instead, Jambois said, "It showed nothing."
What neither Mark nor the investigators knew was that Jensen had left her own testimonial about what was going on inside her home. Before her death, she gave an envelope to Ted and Margaret Wojt. She told them that "if anything happens, give it to the police."
The Wojts, to whom Jensen had confided, gave police the sealed envelope. In it was a letter written by Julie Jensen, accompanied by a photo of a shopping list. Her words were simple and shocking.
"I am suspicious of Mark's suspicious behaviors and fear for my early demise," she wrote. "If anything happens to me, he would be my first suspect. I would never take my life because of my kids — they are everything to me!"
Jensen also discussed in the letter a possible reason why her husband was harboring hostilities towards her. She referenced a brief affair that she had years earlier and said her husband had "never forgiven me." CLICK HERE to read the letter in its entirety.
The shopping list was written by Mark Jensen and included a list of such items as poisons and syringes. Margaret Wojt's reaction to the letter was a mix of sadness and anger. "I don't think you need anything else. Just read this and you know what happened," she told "20/20."
Investigators viewed the contents of the envelope as key evidence and "as Julie's last will and testament," said Jambois.
Mark Jensen had secrets of his own. He had been having an affair with a married co-worker, Kelly LaBonte, and professed his love to her in emails that were found on his computer.
Could this have been a motive for murder? Prosecutors thought the letter and emails would help prove that Mark Jensen had a hand in his wife's death.