Certain things lead me to wonder if perhaps this was an accident, and Lonzie's disappearance was an attempt to hide the body. It could explain the difficulty in pinning down an exact time that someone other than LL or WRE saw Lonzie alive. And if something happened, say, Lonzie fell and hit his head or even found his way into narcotics that were in the home, it would be hard for either Lonna or WRE to say anything, because it would be just as incriminating for one as the other. Somebody is guilty of doing something wrong, but in the eyes of the law, is one more guilty than another? Some people think up elaborate excuses to cover accidents instead of just telling the truth. It doesn't occur to them that the lie is (almost always) worse than the truth. Especially if the lie is designed to shift attention away from the liar.
I could see the accident factor being a big stumbling block, and why Hackney said early on that he had to rely on evidence from someone he didn't really want to rely on. Many of us thought that might be Lonzie's sister, and it could be easy to hide an accidental death from a happy-go-lucky five year old - the baby's sick, he's sleeping now, don't bother the baby...
