Now the motive:
Unfortunately, very little evidence either exists in this case and or is being released. What we do know is that a at least one suspect does exist. So the question comes to why.
The body was found in the residence, therefore it was desired by the killer that it be found or they paniced and stuffed her in the crawlspace either to return and discard the remains or leave it for discovery. My opinion is that the killer paniced used the contractors bags to hide the body and return to remove the evidence at a later date. Why take the trouble to cover a body in plastic if you want it to be found? They got scared after an argument lead to murder and wanted to cover their tracks.
From a forensic standpoint evidence showed she went to McDonalds at 5:40pm and given the possiblity she consumed that meal and since all digestion processes cease at death, investigators should be able to very closley determine the time of death and possibly elimisting suspects and or alibis.
Also we know that leah was strangled. This is a very personal attribute to a killer. A very hands on approach that is almost intimate for both parties. I dont mean froma sexual standpoint, but from a this is a very personal vendetta rage type of thing. If she was strangled manually than it becomes even more personal with the killer using his hands and seeing his victim slip away, again rage. From a victims point of view, they know their killer and are looking him in the eyes, very personal. Yep sickening, scary stuff, but tis the truth. I only make mention of all this to possibly contibute to her closure and of course justice.
She was not sexually assaulted so that speaks for itself. The killer wasnt out for rape or to satify themselves sexually. So, that leaves this: again it was personal, perhaps over an argument of some sort, OR it was a woman who did the deed.
Leahs keys, purse, personal belongings were found inside the apt. so that leaves out robbery or at least single type personal robbery. Assuming that her car was outside, hence the keys was not stolen so that rules that out, however it provides an indicator to the killer that she was home. Since the keys were upstairs in t apt. we can probably assume that the laundry are wasnt locked; was this common or unusual? The door to the alley appears to have a lockset or deadbolt on the door. It must have been unlocked unless the killer had a key to either that door or her apt.
It also appears in the pics that their are at least two basement (grade level) windows. The killer may have watched her through one of these windows and then made his move. My guess would be the one in the alley behind the garbage cans; dark and concealed.