Pleasant Prairie, Wis., April 21, 1999
When Julie Jensen died, her husband, Mark, said he thought she had committed suicide by overdosing on sleeping pills. The initial toxicology report was inconclusive. But police did have one important clue: a letter Julie wrote two weeks before her death saying she suspected Mark was going to kill her.
When Mark Jensen was brought to trial, witnesses testified that he had talked about both planning to kill and actually kill his wife. The medical examiner found antifreeze, a poison, in Julie's system as well as evidence that she was smothered. But the letter was the key piece of evidence that led to Mark Jensen's sentence of life without the possibility of parole. He has appealed his conviction on the grounds that the letter should have been inadmissible.
Click here to watch the teaser of the "48 Hours | Mystery" episode.
© 2009 CBS Interactive Inc. All Rights Reserved.