Rereading the Arrest Affidavit, it is remarkable how little information it contains about probable cause of Chris' guilt. The first one-and-three-quarters page were pretty boilerplate, discussing the original call and the first steps in the investigation. Then at the very bottom of page two and continuing for two more short paragraphs on page three, we get CW's version of the facts, but very little information stating why they believe his version to be false.
Interestingly, CW corroborated what the police already knew when he confirmed the areas where he had disposed of the bodies. Corroboration is important because it helps prevent false confessions. That is why the police never give out all the details about a crime scene. If a suspect knows details that have not been released to the public, then it proves they have personal knowledge, and haven't just read about the crime in the news.
Christopher Watts arrest affidavit