I read some about that too. My mind just started trying to think like AL's might. He was obsessed and proud of his ability to get around security devices, to the point of making "how-to" videos. In order to learn this he had to practice on the actual devises to perfect his skills. If he acquired a lockbox he would have one to practice the skill of unlocking the device, perhaps with his magnet technique. He could easily enter homes for theft. Here is an article about that very thing happening in the Little Rock area.
http://firstarkansasnews.net/2011/08/lockbox-thief-caught/
Again, that is just a brainstorming idea when trying to think of a motive and recalling that the media said the door was left open and the lockbox was missing. It just doesn't seem like he would have bothered taking it while struggling to get his victim out of the house in a hurry.
I still lean toward a kidnapping/ransom gone wrong. I do not think a sexual assault would have been the main motive since he seemed to have no shortage of connections for hookups using his dating/meeting/trolling websites. Granted, that isn't all that is involved in a sex crime, but it just doesn't add up for me.
He seemed more motivated by acquiring goods. He needed money. Since he didn't take her purse, an intended ransom is still at the top my list, with her murder being an accident in the committing of that crime either because she could identify him or because in his effort to subdue her, he killed her .
I also wonder if BC's wedding rings or other jewelery could have been found at CL's house. It doesn't fit with his greed to leave those behind with her body. Those that knew her say she loved "bling" so I am guessing she had some valuable rings.