I know Kolars book points to BDI and plenty of really intelligent people here lean BDI. After reviewing Kolars book several times, in particular the interviews with BR, I still have doubts.
While Kolar saw all the evidence, so did Michael Kane (prosecuting attorney), and Kolar and Kane came to different conclusions. In fact Kane was both shocked and angry that some tabloids were turning their attention to BR. And Kolar himself seems to consider a charge of kidnapping (which does not have a statute of limitations) might be able to be applied (to JR). Nonetheless, I try to be open to a BDI and listen to what people say about it. Perhaps BR was part of the whole scene that night, and it began with a fairly routine skirmish between BR and JB.
The behavior of PR and JR on the morning and early afternoon of the 26th was one of the things that made me believe the two of them, both JR and PR were involved in JBs death. One perp and one covering, or two perps - IDK. Their behavior was surreal.
1) JRs carrying JBs stiff body (in rigor) and asking Det. Arndt if JB was alive.
2) PR not responding to the commotion, and one of PRs friends has to escort her in to the living room to view the situation with JB. Then PR, ever the dramatic, throws herself on the body, raises her hands to God asking for a Lazarus intervention, then rolls around on the floor, hysterical.
3) Of course, JRs rush to get out of Dodge.
These were actions which, imho, speak of both of them putting on a show and running for their lives. And what do they do with BR, but send him out with a neighbor, not allowing police to question if he heard anything. For a time, they even had guards in BRs classroom (under the guise of protecting BR from the evil intruder, but my view is to make certain he wasnt questioned by classmates.)
To the ongoing question, why would one of them cover or assist for the other: There are too many reasons to list and they all speak to dysfunction, which includes lying to themselves, to each other, and to the outside world. Consider Philip Garrido and his wife Nancy convicted for kidnapping and the sexual bondage of J. Dugard. Garrido could not have succeeded in kidnapping and holding J. Dugard in captivity for 18 years without his wifes assistance. Both JR and PR had their demons.
Its possible that PR might have spilled the beans initially, but JR and Dr. B kept her in a very drugged up state. PR then kept quiet as she likely knew full well the implications of her actions, even if BDI: Accessory to murder after the fact is what she and JR could have been charged with if BDI. But possibly PRs eye may have been on the future too - the chance return of her cancer and what would happen to BR. And, just like N. Garrido, PR may have been loyal to JR to a fault.