You know, its not completely out of realm of the possible that these people are lying and really know much more then they are telling police.
I am not implying anything about these people, but I am just saying it isn't impossible.
I lived in Las Vegas for a couple of years and was involved with some people who, from the outside, seemed like very normal folk...in fact, in many ways, I was someone like that, too, due to issues I was fighting at the time.
We all have a different set of experiences in our lives, and, unfortunately for me I suppose, my experiences make me think about this in a different way then many here might.