Sorry but they do.
Instinct is what guides them.
EVIDENCE is what proves the case, but INSTINCT is what tells them where to look for the evidence.
We now know that we have some posters on this thread who are/have been actively involved in investigations of one kind or another, and they will ALL tell you that instinct is one of their major tools.
This is why we have so many cases (eg Casey Anthony) where blind freddy can tell what has likely happened, but the perp goes free...no EVIDENCE.
Would they have chased the Anthonys so hard if it wasn't for instinct? Nope. The EVIDENCE just wasn't there.
Jonbenet, another one. Most Americans believe the parents were involved. Again, not enough EVIDENCE (debateable) or at least, not enough to bring charges and make them stick.
ETA - a snippet from msm on the Isabel Celis case, where the search warrants are still sealed -
Police may not know for sure what happened in the Celis house the day the six year old girl disappeared but search warrants may offer their theories.
A search warrant release often includes transcripts of detectives convincing the judge to issue the warrant. They tell the judge what they think they may find. After the search, detectives report what they did find.
http://www.kgun9.com/news/local/160916585.html