It's time for Sills to have another press conference. This press conference needs to be a little different than the last ones he's had.
This time he needs to sit down and present all the evidence they do have, explain where it came from and what it means. He needs to present pictures, maps, and timelines in very basic forms. He needs to detail what kind of boat they are looking for, what kind of car they are looking for, and what kind of evidence he has to back up those suspicions. Any information about the possible perpetrators that hasn't been released to date.....now is the time.
Somebody out there knows who committed this crime, and they may not even realize that they know it. Some of the evidence that Sills is hesitant to release publicly might well be evidence that jogs someones memory about what they saw that night, someone's behavior after the crime, or some small detail that only one or two people may know about. Just lay the facts out there and let everybody take a good hard look at them.
If they continue to withhold information, continue to keep things enveloped in a cloud of secrecy, continue to give only carefully crafted answers, then I'm afraid when it comes time to hunt the file folder down inside the filing cabinet, just look for the folder labeled "UNSOLVED".