Why hasn't the possibility that Col. Shue may have led a secret life ever been investigated? According to Tracey Shue, her husband 'left for work earlier than usual' that day to 'catch up on paperwork'. This point seems to have been readily overlooked in reports.
Why couldn't it have been that he left early to meet someone before going to work? Not someone he necessarily knew very well but someone who was interested in the same, well, 'pleasures' ... and the 'meeting' turned unexpectedly and seriously out of hand?
I certainly do not intend to smear the Col.'s reputation, but the possibility should at least be ruled out, just to be complete.
Or, maybe he was intercepted at random by a psychotic?
What if the removal of certain body parts from the Col.'s body might have been an over-zealous psychotic attempt to remove saliva-covered (DNA) skin or to collect souveniers?
Regarding the 1st wife (Nancy) pleading the 5th, it is her constituitional right. She may have at one time or another bad-mouthed her ex- (the Col.) in anger with no intent beyond that and if she proceeded answering questions investigators most certainly would throw past utterances back at her. Either way, it was a smart, well-advised move.
As for the 'threatening letters' ... were they received via mail? Left on a door-step? Car window? Dusted for prints? Checked for DNA?
Just my ­2¢.