Thanks Sami - appreciate the input. I have gotten quite interested in how far from the body evidence would/could move. I am thinking along the lines of the possibility that JY would have changed clothes in his own bedroom and think there is a possibility there may have been some blood evidence found in the closet, maybe on the clothes or shoes on the floor of the closet.
If he was careful enough, the only blood evidence would be on the clothes he grabbed to change into in the form of trace elements. Unless he's stupid enough to grab coathangers. As I said in my other post, the is a chance that the perp would not have much blood on him at all. So he may have just wiped his hands on the 'murder' clothes before changing, but that would still leave trace evidence on his hands and would certainly interfere with the natural oils on his hands. But I would agree, there si a possibility of him changing at the house.
I also wonder about Strach's idea that the clothes worn during the crime were put in a plastic bag and taken by the perp. I wonder about possible patterns left on the floor where these clothes may have been placed while changing - wondering if that would be identifiable if there were no dog or child present to track through.
Now here's another area that could get interesting. It would say a lot if he put the murder clothes in a plastic bag. If he took the plastic bag upstairs before the murder, it could mean either that he had the intention of causing bloodshed before he even went upstairs or that he intended to take extra clothes (aka moving out) and things went horribly wrong after an argument.
To go downstairs and get a plastic bag would certainly mean that he spent a good amount of time after the murder in the house, but the murder clothes wouldn't necessarily even touch the floor if he put each item into the bag as he took them off. But both mean that he would've cleaned himself up inside the house.
I know with luminol that LE can often find tracks that show how an area was left - thinking it may be possible to figure where the clothes may have been left while changing. I'm thinking luminol would have been used as the very last part of the scene investigation after LE felt all forensics were collected, as from news reports LE was at the scene at night.
Thinking on all this and remembering that this house had four other owners, there was a child and a dog loose in and around the house,
I'm still not sure on the dog being inside. Regardless of being a family pet, I've never seen a dog that would not be curious as to not enter a room where there is blood. Even a loving pet would lick it's owners face if she was found on the floor and would certainly have no problem 'helping' with a clean up of blood on the floor, although it may not touch the body itself. I would also think that Meredith would've mentioned the dogs pawprints as well as Cassidy's...but that just my opinion 
because if it was particularly attached to Cassidy (sleeping with her etc) it would've been right beside Cassidy next to Michelle's body.
I'm starting to be able to explain in my own brain (rightly or wrongly) why this scene may have taken so long to process. Very complicated scene I think. Do you yourself have any idea what the "special machine" brought to the house might have been (maybe fairly new technology)? Some kind of spectral imaging maybe that would not destroy forensic evidence as luminol does?
It could have been anything from a vacuum sweeper (a vacuuming machine which has a special filter attached) to different lighting sources, ie; uv or laser. Some lights show up blood traces, whereas some will show up an area that has recently been washed down and some show up chemicals that may have been used.
The length of time taken depends on how much forensic evidence they've gathered from the scene. This crime scene probably involved collections of...
hair
fibers
skin scrapings
blood (pooling, drops, spatter, runs, arterial sprays)
finger/palm/hand prints, either complete or incomplete.
vegetative matter
other bodily fluids. vomit, seminal stains even if no sexual offense has taken place, saliva, amniotic fluids (since Chelle was pregnant at the time)
plus inanimate objects (lamp etc)
One other - the location of this house between two others, tends to make one wonder why someone would decide to enter this house - from the aerials - there would have been much easier "targets" for an intruder to be inticed by - would you agree?
Yes I would agree from looking at the aerial views of the house. After the majority of the scenarios I have done so far, I tend to believe that Chelle was the target. Even if a burglar had gotten into the house, in all honesty he had no reason to go upstairs at all. Her purse was apparently downstairs in the kitchen, all expensive items of value apart from jewellery would have been downstairs, so he could've gotten a 'very profitable grab bag' just from downstairs without having to disturb the sleeping Chelle upstairs, if she was asleep.
Know you are probably busy so not to worry about my rambling around.
Having fun with baby C ?
I just bet you are !
That is the variable, how astute the forensic team is. 
