RSBM.
This, in particular, is something that I find significant. At the time LE would have been well aware of what time in the video the still images of BG came from and the time within the video that "Down the hill" was spoken. The difference in time alone would be adequate evidence to know if there was another person involved. If the amount of elapsed time would make it either impossible for BG to have covered that distance to the end of the bridge or if it indicated BG had to run or double/triple-time it to get to the girls then there has to be more than one person involved. It is quite clear from the audio that BG is not out of breath or even breathing heavier.
Everything is significant until it's proven not to be in a murder investigation. When BG was not apprehended shortly after the murders, it tells me that he lives a life with little exposure to society, although, by no means is he a hermit.
LE knows whether or not more than one is involved for the very reasons you mentioned about the recording and also because of the scientific discovery known of as DNA.
My key question is why it was that Libby was concerned enough to start recording but not make any attempt to get out of there. Remember there isn't anything indicative of immediate threat in the images of BG at that time in the video where the still images came from which was already after Libby determined she was concerned enough and needed to start recording. Since the speaker of "Down the hill" was not out of breath we also know he didn't have to chase after them.
It is enough for me to know that a crime was about to commence when Libby captured the image of BG as she was backing away from BG while at end of the Bridge.
So, for me, that leaves two possibilities. Either Libby was concerned enough to record but not concerned enough to try to get out of there and simply waited for BG to walk to them or there was one or more individuals involved aside from BG and were near the girls while BG was still on the bridge - Thus, it wasn't BG keeping them where they were. I believe strongly that there is at least two individuals responsible for the murders or Libby and Abby.
Many have questioned why the two girls just didn't make a break for it and take off running. I think we know the answer. The girls were trapped. Someone was waiting at the end of the Bridge as BG approached. Perhaps, it is his no nonsense, controlled voice that we hear.
<> Yet, LE has not made such a declaration even after all this time. I don't understand why it is they would leave something this significant dangling out there.
I do not understand why LE does not become clear about some facts just as GH is doing with his new debunking videos.
There is admiration in GH's work. His skillful productions were tremendously helpful for the Long Island murders, McStay murders, and Travis Alexander's murder to mention a few.
I hope everyone realizes GHs Flow of the Crime Scene is based on his opinion. GHs Crime Scene Flow videos have never once been verified by LEO. However, his videos will continue to be beneficial for many other reasons.