There's no concern with DNA in moving the body because the person would obviously already be covered in blood. Who returned to the scene? Mere speculation, evidence of this - zero.
The precise site of the murder could reveal a multitude of clues. Footprints for a start, blood from the killer if he got cut during the attack, a dropped key, a torn fibre from their jacket or shirt, their hair if it got pulled at any point during a struggle. You are not going to find any of that if you don't know where the murder took place, which is why the body was moved.
If you still think Mitchell carried out this murder, then had the foresight to move the body to confuse the Police and prevent them finding anything incriminating, as well as then somehow managing to appear normal 40 minutes later with no signs of being in any type of incident and no trace of any blood on him or in his house, then I can't help you.
You have a fertile imagination, WW, I'll give you that. However, I think your theories are very illogical -- bordering on the absurd -- as I've said & argued previously.
Btw, regarding your contention that whoever the killer was likely had to be heavily and conspicuously blood-stained, why didn't the 8 separate eyewitnesess (ie, LF, RW, DH, GE, AH, CH, MO & DH) who saw that shifty-looking youth standing himself on NB rd between 1740 - 1820 say in their statements that the youth was covered in blood? Not one of those 8 witnesses mentioned anything about the person standing on that road having blood on them. And who do you think this youth was that those 8 witnesses saw? Finally, do you know that Professor Busuttil himself, when he was first summoned to the locus, during the early hours of 01.07.03, said that it was entirely possible that the killer avoided becoming heavily blood-stained if they cut/slashed the victim's throat from behind?