You know, I don't have an airtight theory. Just some opinions.
I think the graverobbers are a dead end, which I think is an opinion shared by the majority of those who follow this case. I think that the ONLY way that they could be relevant is IF one of them was involved in either drug trade or a gang, and there was a fear that SS's testimony would lead to deeper problems. To my knowledge, none of those 3 have ever been linked to a gang or drug ring, and I think this particular theory is one of the lesser likely ones. Even if this were the case, surely whoever would have been after SS would have had a chance to get to her more easily at some point while she was alone, rather than risk breaking into a house with a driveway full of cars. I just don't really buy this theory. I mean, it is always fishy when someone who is scheduled to be a witness for a trial goes missing shortly before the trial, but that being said, this isn't in my top list of theories.
I've always been intrigued by the fact that SG knew enough "withheld" details about the case that he was so readily believed and that gag orders were issued surrounding some of the investigations that came as a result of his tips. I don't necessarily believe that he did it, but I do think that maybe he had contact with someone who was involved, and therefore had at least some real information.
I think GC could possibly be a good fit. The rumors that he and SL had dated (or at least had some form of relationship) combined with his history of violence towards women definitely puts him on my short list. He also had some pretty sketchy people in his employ at the time of the crime. Had he needed help, I don't think he would have had much difficulty finding someone in his circle to pay off to do so.
Edited to add: I find the link between GC and SG through Dykes fascinating, especially when you start digging about some of the places where the police searched and how they can be directly tied back to this trio. I think that could possibly explain a few things, and while I think that maybe some of this has gotten derailed into the realm of fantasy and conjecture in the past (those who read on other message boards know what I'm talking about!), I have no problem with the idea that there could be some genuine information there.
I've gone back and forth on RCC. I think most of what he has said it just blowing hot air and toying with LE. At this point, I just don't think he was involved.
So, all of that to say that I don't necessarily think I have a scenario put together that involves a hard view on one of the top suspects. But, I do think I have some theories on WHAT happened that night, even though maybe not WHO.
I think that SL was the intended target. To me, this is all that makes sense. SS was not supposed to be home that night. SM was only there after a convoluted series of events. I don't think either of them being targets makes sense. If someone was after SS, why not wait until she was alone rather than break into a house with a driveway full of cars? Same for SM. I would think if someone was following SM and after her, seeing her go into a house accompanied by a friend while seeing other cars in the driveway would not strike them as being the prime opportunity to take her. I think that the most likely scenario is that the perp was already in the home with SL under control when the girls got home (this would make sense that the perp had entered and gained control while SL was home alone, a much more opportune situation for a crime than a house with a driveway full of cars), and the girls then became collateral damage. It would make sense that they went to SS's room and got ready for bed, maybe were even laying in bed talking (since some reports stated that the bed looked slept in) while SL was restrained in her bedroom. I don't imagine this would have been difficult, as the perp could have told her that if she was quiet, they would leave after the girls went to bed, but if she made noise her daughter would be killed. In that scenario, either SS heard something and went to check, or she decided to go peek in and tell her mom that she had decided to come home with a friend since the plan had been for her to spend the night with someone. At that point, the perp just needs to have the gun to SL's head and say that they are all going to leave quietly and go somewhere to talk, and if anyone decides not to cooperate, mom dies. The idea that one person with one gun could have had control over all 3 of them no longer becomes difficult in that scenario.
I don't think they were killed in the house. I don't think their bodies are buried in concrete at a construction site (hiding 3 bodies in the middle of town at a construction site would have just been too risky). I think the bodies were either dumped in the woods somewhere (we have no shortage of dense woodland!) or in one of the many lakes around and sunk using cement.
Lastly, I do think that LE knows (or at least is 99% sure) about what happened and just can't prove it. We KNOW that there is information about the case they haven't made public. I think the case is, for the most part, "solved" but not prove-able. I think they are waiting for someone to come forward with something that would let them bridge that gap. Perhaps that is why, after all these years, there is still some information being kept from the public. Still relevant details that have not been discussed despite the recent 20th and 25th anniversary specials that have aired locally. I do know for a fact(as I said, I'm new to commenting, so I'm not sure how much detail I'm allowed to give with this type of stuff) that some of the rumors about SL going around at that time regarding some of the things she was involved in were thoroughly investigated and that the rabbit trail from that investigation did give LE some interesting information (please know that I'm not trying to paint SL in a bad light at all or accusing her of anything). It is one of those things where I have been involved in conversations with people who were part of some early questioning, so that's how I know some of what questions were asked and what information was gained. I'm not trying to make it sound like I have some sort of inside information, because I don't, it is just that one of my circles of people involve a couple of individuals who were, sadly, only one step removed from this case.
That got really long and not all that helpful, but that is the basics of where I land with this as of today.