I love the word schlemiel.
I agree with your observations -- I think that the entire night was likely a series of poor judgments, not malice and that continued when JR, CR and MB decided to withhold information about what happened that night.
Unfortunately, I don't think that anyone had to be a criminal mastermind or full of malice to hide Lauren or keep quiet, so the personalities of the guys at 5 N don't reassure me that they are not responsible. If anything my feeling is that they are kids who haven't really ever taken responsibility for anything, are still under their parents' control and probably don't want to disappoint them. After watching JW's parents in action, I realized that even if any of them wanted to step up and take a different course of action, it would probably be hard to do. The POI all have people surrounding them whose main priority seems to be protecting them from any consequences.
[ETA: Didn't jslicht also say or imply that jay had been in trouble in the past and that his father probably anticipated that he would need legal help or something along those lines? I don't want to go back and read those threads again, maybe you or Ros know?]
Again, I look at DR in comparison. All he did was take a police poly, but it put him in a totally different light, IMO.
I don't recall anything on PT about Jay's previous legal problems, but if you search on his full name (Jason rather than Jay) at mycase.in.gov you can find out about his previous run-ins with Bloomington LE.
The other thing that puts DR in a different light is the presence of cameras at Smallwood and therefore video that corroborates his story. If there had been cameras at or near 5N, we might not be having this discussion.