You may not get this but Dinse is saying they are not bluffing about Ricci's involvement, they believe he's involved up to his hairline but their case is not solid yet. This is why they made the statement at the same time they do not plan to make an arrest until they find Elizabeth or her body. They don't want to try this dirtbag and not have 'beyond a reasonable doubt' evidence then find Elizabeth or her body with the conclusive evidence and be locked out by double jeopardy.
What I really don't get, is why I'm replying to this post.
You and others bent on pinning this on someone you consider inferior, might wonder why Ricci would attempt this sort of crime? What's in it for him? No ransom involved, an almost sure trip to prison for life -- or worse, considering his record, and maybe MOST IMPORTANT OF ALL, not nearly enough time to commit the deed in the reported time frame.