I've wondered about this for a long time. That 6:05am call has always intrigued me. I wonder if that may have been the original alibi call, but something didn't go according to plan (timing / location ended up being off and/or potentially incriminating), thus the need to set up a 2nd call and make a 2nd trip to the store. Just one thought I've had ...
Hi TXr... We're dealing with a malicious mind; malice and aforethought ... AFORE .. being the proverbial prefix here. Like you, I also think his preparation went somewhat awry. Unless we're the killer BC himself, we may but only speculate.
So here's my theory, fwiw ... :
There may have been a much longer, tougher struggle than he anticipated in the hall, for all we know; hence missing ducks and sticks, rugs and things. May have been more bodily fluids and feces than he anticipated; place was a mess - taking longer for BC to clean. He may have used all detergent in the house - urgently needed more - headed to the store. Time was running out... his heart was pumping... he knew he'd be caught on cctv ... needed a quick-thinking cover for the unforeseen "new" tactic... as in: why would he be at a store @ 4am ish?
"Ahhh! kids!"
He knew where he was going to dump NC, we now know that. It may have been getting light; he knew folk would be out walking dogs, running, going about their business. May have initially decided to have hidden NC deeper in the ditch/woods - but by then ... time not on his side.
Fear of discovery - dumped NC and scrambled away; afraid his car would be seen, and just in case it was, he decided to call himself at 6.05 - and head from the dump site-then on to dump evidence carried from house to the car - and then finally return to HT (changing clothes in car, which had planned to do anyways). Evidencing that "call" would explain why he was driving around after 6, and why he was back at HT.
"NC asked me to go back for milk and juice...". But - he was in different clothes and shoes within such a small time frame.
Plausible - any sighting accounted for, (in his mind). He didn't even have time to consider her earrings and may indeed have taken jogging shorts but had no time to finish the "scene" to look like the random attack he'd planned - so he dumped her shoes and gear with other evidence from the house. He concentrated on speed - not detail. Didn't realize he had two left running shoes; didn't realize robbery a motive for the attack if no sexual assault evidenced. (Bet he kicked himself for this, perhaps within hours of dumping the body... JMO)
The above para makes me think the last thing he did to NC, moments after she passed, was to snatch that necklace - well before moving her body from the house. And I can imagine his expression as he did so.
So ... what went wrong for BC? IMHO only ... time, tools and attention to minute detail. The length of time it took for NC to actually die; the length of time to clean; the time of the early hours before dawn broke.... and unforeseen extra cleaning materials required; unforeseen extra items to get rid of such as ducks, sticks etc., ... and overseeing final-scene detail.
Time, tools. Essential ingredients for any project - after the plans have been approved, of course. Just my take 'n thoughts...