There are other cases where they were thinking it was a person that it turned out not to be, but this just seems out of this world obvious. LE themselves said that the other skull looked much older. They both were obviously murdered by the same person and were last seen with the same person... JMO, there is a 99% chance that's Kara, her mother thinks so too. I'm just hoping they don't find another set of remains meaning he had a chance to do this to some other innocent girl.
I'm worried that the small amount of evidence we know they have isn't enough... As far as I know, they only have the restraining order Kara had against him in high school and they fact that they were dating at one point, and knowing he was the last person seen with Jessica and charged with burning her car. I'm really not sure if that's enough to get a conviction, although if there was a jury I think he'd be pretty screwed. JMO.
I hope if there is a plea deal it just means the death penalty is off the table and he has to rot away in his cell for the rest of his life.