The prosecutor in a high-profile Duluth murder case 26 years ago says tests of DNA on an old envelope confirm the prosecution's case. From the beginning, authorities suspected Roger and Marjorie Caldwell of entering Glensheen mansion and killing Duluth heiress Elisabeth Congdon and her night nurse Velma Pietila. As Elisabeth's adopted daughter, Marjorie Caldwell, stood to inherit a substantial sum from Congdon's 8 million dollar estate. Roger Caldwell was convicted of the murder and Marjorie was aquitted. She was later convicted of arson in an Arizona case and is still serving time. Caldwell committed suicide in 1988, but maintained innocence in his suicide note. John de Santo, one of the prosecutors in the murder case, has just co-authored a book called "Will to Murder." He says new evidence proves the couple's guilt.