I think that four things are probable.
1) They would have gone in one car. The other two cars would have logically been left at Janelle's house which offered better parking in a better area. There is no logic in believing they would have taken more than one car. I would have never left my car anywhere when I was 18.
2) They could have overnighted in Battlefield but chose not to. This suggests to me there were underlying reasons for the change in plans. If so, what were they? And we can probably assume, although I hate to do that, they had some adult beverages so the 11 mile drive was somewhat hazardous. They could have stayed there, but it definately would have been easier to go home. A crowded house versus a 10 minute drive to my bed is no match. I would have gone home. We also have never known how drunk or sober these girls were, we can assume that they had been drinking, but to excess? We have no idea.
3) I believe this was a planned event which brings up the obvious question. What was the motive? And as stated, if either Sheriill or Suzie remained alive they could surely point to a perpetrator(s) as they were very close as mother and daughter. That suggests the killer or killers waited until Suzie was home to strike as Sherrill was available nearly all night long. A planned event has some problems. We do not have a motive for a planned event. Why go after 3 women when 1 is the target? I also think that if someone was going into a house with 3 women, then the phone lines would be cut. There is no feel for a pro hit to me.
4) The purses were forgotten with the money. The television was left in haste. The door was unlocked in the rush to leave. And the globe was broken which probably spooked the perp(s) to leave immediately since it could have been heard and daylight was fast approaching. It would have been to the perp(s) advantage to have taken the purses, turned off the television, locked the door and cleaned up the broken globe as it would have delayed discovery of the crime scene. That suggests to me that the final victim may have been the one who kicked the globe off the wall breaking it which forced the quick exit. Had that not happened, I believe it would have been much wiser to have taken the purses, turned off the TV, locked the door and simply left with all three victims. There was no logical reasons to have overlooked these four clues that something was not right in that house. If it were a pro hit then yes it would make more sense, but if it were something different, and by people who were in a hurry to get out of town quickly, I could see all of that being left that way.
Going to respond to both of you at the same time, just to get the conversation going again.
1. The "one car" scenario is interesting. It's pretty clear that the trip to the water park would have involved kids in a group going in one car (or several cars if others not usually mentioned were involved). So, in theory, "leaving a car" would have been done the next day. Now, I can see why Stacy would have wanted to take her car to Susie's, just because most of us, given a choice, prefer to have our own transportation available ust in case something comes up. I know I sometimes drive myself when I could ride with other people because I want to be able to leave or stay based on my own preferences. So it doesn't surprise me that Stacy would take her car AND that later on she might ride with a group for an all-day trip.
2. I am never surprised when teenagers' "plans" change. Lots of their 'planning" is more wishful thinking than everything else, especially on a night like graduation, which they start out imagining as "anything is possible" only to encounter realities like family expectations, the difficulty of getting a group together after a big event, fatigue, lack of money, and parental objections. So I take the changes in plans as having more to do with "reality setting in" than anything else.
3. I don't think there is any need for a "motive" other than the pleasure of killing, controlling people, or whatever else leads psychopaths to do what they do. If there is a "motive," it is probably too sick for normal people to understand. The bottom line is that someone was bold enough to abduct three women, and apparently from the home where two of them lived. There are precedents for the abduction/murder of multiple women across generational lines: Carole Sund, her daughter and her friend; the woman and her two daughters who were lured onto a boat in Florida while on vacation; the home invasion in which a doctor was attacked, his wife and daughters were raped and murdered, and the house set on fire. Every one of these crimes were random, in the sense that there was no relationship between the victims and the perpetrators. That does not mean the abduction was not a planned event--in the sense that a predator is always looking for prey and has made preparations in advance. What might not be planned is the
seeming opportunity that triggered the abduction.
4. I have puzzled long and hard about the purses. All that tells me now is that money was
not a motive or the money would have been taken. My guess is that the man or men who did the abduction didn't give a second thought to the purses. Why would he want to take them, when that would mean the need to dispose of tremendously significant evidence linking him to the crime? Think of all the abductions in which cell phones, purses, wallets, and other personal items of the victim are left strewn across the landscape or found in dumpsters. No, the purses only matter to us because the first people who came in the house saw the purses, cigarettes, etc., there and that did not match up with the women having gone to breakfast or out for coffee or shopping. Then our sleuther minds get busy and we imagine the perpetrator staging the crime scene and then ask "Why did he/they leave the purses?" Because the perpetrator(s) were not stupid. Whoever did this did not need to stage the crime scene. Taking the purses might have bought another hour or so, but with teenagers involved, the chances of the alarm going up early was very good and leaving the purses caused just as much confusion. I think it is far more likely that the abductor(s) was/were far more interested in getting the women into a vehicle and away from the house on Delmar. As Mark Klaas says, a loved one can disappear at the rate of 60 miles per hour. If the abduction happened even as late as 4 am, the perpetrator(s) had 4 hours to work with. The purses weren't a factor.
And in any event, Janelle, her boyfriend, Janis McCall and a bunch of other people screwed the crime scene up by moving things around anyway.