(CNN) -- The Wisconsin man accused of poisoning his wife with antifreeze and convicted of murdering her was sentenced Wednesday to life in prison with no chance of parole.

Mark Jensen's chin quivers as a letter from his sons is read in court Wednesday before his sentencing.

Mark Jensen, 48, was found guilty Thursday in Elkhorn, Wisconsin, of killing his wife, Julie Jensen, in 1998.

The prosecution said the murder culminated years of torment.

"Your crime is so enormous, so monstrous, so unspeakably cruel that it overcomes all other considerations," Kenosha County Judge Bruce Schroeder said before pronouncing the sentence. Watch the judge lower the boom »

Prosecutors contended that Jensen poisoned his 40-year-old wife with antifreeze and then suffocated her in 1998, but the defense argued that Julie Jensen was a depressed woman who killed herself and framed her husband.

Julie Jensen had given a neighbor a letter pointing an accusing finger at her husband should anything happen to her.

She also made foreboding comments to police and to her son's teacher, saying she suspected her husband was trying to kill her.

Her letter, read aloud in court, said in part: "I pray I'm wrong + nothing happens ... but I am suspicious of Mark's suspicious behaviors + fear for my early demise." Read the letter »

The case turned on the admissibility of the letter, which would have been considered unusable "hearsay" evidence if Schroeder had not ruled that it was a "dying declaration." In such cases, the defendant has no opportunity to face his accuser.

After the verdict, jurors told reporters that the letter gave them "a clear road map" to conviction, as one female juror phrased it.

Another female juror said he believed Mark Jensen was trying to push his wife over the edge. "He tortured Julie hoping she could be classically diagnosed as a nutcase," she said.

Several of the jurors were in the court gallery for the sentencing hearing Wednesday.

Jensen, dressed in blue jail fatigues, sat stoically while Julie Jensen's four brothers asked for the harshest possible sentence.

"I hope the court shows the same mercy and compassion that the defendant showed our sister," Patrick Griffin, the victim's youngest brother, said. Watch brothers demand justice »

But Jensen's chin quivered and his eyes watered when his attorney read a letter from Jensen's two sons, David and Douglas.

"He never failed to support us throughout this ordeal," the sons wrote in requesting mercy for their father. "... If anyone in this world is the epitome of loyalty, it is our dad." E-mail to a friend

CNN's Jim Kavanagh contributed to this report.