"They didn't find a body....they found a skull."
The body was skeletonized. We all know that. Don't parse words.
"A skull that had been tampered with by the meter reader."
Even if true, and it's only speculation, what is that supposed to change? That makes it an accidental death? Be serious.
"The only thing that could be said _with certainty_ was that duct tape was found with the remains."
"As to where the tape was placed on the body was pure supposition.
Certainty isn't required. Beyond a reasonable doubt, remember? And no, the tape was wrapped around the head. There was testimony about the fact the tape was what kept the jawbone and the skull together.
"Yeah....it's a shame that the evidence was lost in that fetid swamp....but lost it was."
Sure, some potential evidence was lost. But there was still enough evidence to prove a murder, and that Casey did it.
The prosecution went to great pains to demonstrate that the duct tape, if properly placed, was just wide enough to cover both mouth and nose.
Covering mouth and nose is murder....covering the mouth but leaving the nose exposed is an attempt at silencing. So that the skull was tampered with and the position of the tape now indeterminable means a great deal indeed.