I find it particularly interesting that there is a total lack of DNA based evidence either at the MacPhail house or at the home of the accused. I also think it is highly unlikely that the home of the accused could be cleaned to the extent that absolutely nothing of what might be there in the first place would remain. It is incredibly unusual.
Furthermore, if it was the case that the accused was hyper-aware of leaving DNA evidence at either the MacPhail house or his own home, then it doesn't fit that he would be so utterly careless with respect to leaving traces on the actual victim.
It's impossible to tell without knowing the details, but theoretically the 14 points where DNA is noted on the body could all be related to semen ?