ELKHORN, Wisconsin (CNN) -- Every time Julie Jensen's brothers hear the letter read, it brings everything back. They say they wonder why their sister didn't tell them about her marital woes and how tormented she might have been in her final weeks. Even more, they wonder if they could have saved her.

"I hear her voice every time I hear the words in that letter," said Jensen's brother Paul Griffin.

"If she would have come to any one of us for support ... we would have helped her."

Griffin is referring to a note written by Jensen on November 21, 1998. It was in a sealed envelope she gave to a neighbor with instructions to turn it over to police if anything ever happened to her. Twelve days later, Jensen's husband, Mark, found her dead in her bedroom, and the neighbor handed the note over to police.

A decade later, Mark Jensen is standing trial, accused of poisoning his wife with ethylene glycol, commonly used as antifreeze.

The defense says she killed herself and blamed her husband. As a result of a rare legal ruling, prosecutors are allowed to use the letter as evidence.

In the note, Julie Jensen says that her relationship with her husband is deteriorating and that "if anything happens to me, he would be my first suspect." She also mentions having an affair seven years before then.

"I pray I'm wrong + nothing happens ... but I am suspicious of Mark's suspicious behaviors + fear for my early demise," the letter says.

It ends with her mentioning her love for her two sons, who were 8 and 3 at the time, as well as her husband.
Letter from the grave, "She believed in Mark as a person, as a husband. She wanted it to work out," said Patrick Griffin, the youngest of her four brothers.

Patrick said he constantly tries to put himself in his sister's shoes and what must have led her to write the letter. "I can't imagine how scared she was," he said.

Prosecutors allege Mark Jensen wanted her dead so he could be with his mistress, whom he has since married. But defense attorneys maintain that Julie Jensen had been treated for depression -- including just days before her death -- and killed herself to get back at her husband.

"Finally, after nine long years, Mark Jensen can clear his name," attorney Craig Albee told the court in his opening statement.

There have been many legal twists in the case. Mark Jensen wasn't arrested until 2002 when prosecutors felt they finally had enough evidence to prosecute.

That Julie Jensen's letter is even being allowed is a rarity. Such letters are generally not allowed in court because a defendant has a right to cross-examine his accuser. But the Wisconsin Supreme Court ruled that right was forfeited because of probable cause the defendant, Mark Jensen, prevented the witness from testifying.

And so nearly 10 years after Julie Jensen died, a jury is hearing arguments about her death.

The prosecution argues that she was weakened from poison and ultimately suffocated with a pillow by her husband. The defense strongly disagrees, saying the suffocation theory came up only after an inmate jailed with Mark Jensen was given a lesser sentence to testify against him.

The trial is expected to take up to two months. Julie Jensen's four brothers are attending the proceedings in Walworth County, Wisconsin. Mark Jensen's parents are also in the gallery.

Mark Jensen faces the possibility of life in prison if convicted. His and Julie's two sons, who are now 17 and 12, live with their stepmother while their father remains jailed without bond.

Paul Griffin says he hopes his sister's husband is held accountable. "In the words of his defense lawyer -- finally. I get to say finally," he said, fighting back tears. "Julie's voice is going to be heard, finally."