I'm in the "They know who did it but do not have the 'green light' (whether evidence, admissions, etc) to proceed" camp.
I just watched a program last night that aired at 9pm (20/20 type show, don't remember the name of the show) where the murderers weren't arrested for 15 yrs. But they did end up in prison for the rest of their lives.
And, I maintain that the "life" Nevaeh's murderer(s) are living can't be too fulfilling. They MUST be looking over their shoulders at every turn. Somewhat of a "prison" already.
I don't think LE cares one bit about the public's demand to know details. And they shouldn't.
I want them to take their time, get it right, then pull the trigger. The damage has been done. There's no need to rush just to satisfy the public and possibly screw something up and lose everything.