Carbuff,
The "girl in the canyon" (I assume you mean the Jane Doe) was found 500 ft from Campbell and Anderson. This was no urban dumping ground. This was a very remote spot off a side road in the high desert country of SE Idaho. In this area, there are hundreds of miles of back roads, thousands of miles of ranch road and very few people to notice anything. The odds that two predators would independently choose the same dump site in such an expansive area are infinitesimal. The same perp did all three.
Jane Doe was not a local girl. She could have been a transient; a hitchhiker or something or she could have been brought there from some distant area. Her murder was obviously different from Campbell/Anderson but that doesnt mean her killer was someone different.
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We know that Royal Russell Long abducted and raped two young hitchhikers. Everything else is speculation. He has been identified as the guy who lured two 13 year olds from a carnival in Oklahoma with the promise of a chance to earn some money. He lived in Rawlins at the time Carlene Brown and Christe Gross disappeared from a Rodeo but we do not know anything about the circumstances and there is no evidence that I am aware of that Long was at the scene. Jayneel Banker was abducted from a Rodeo. The fourth girl, Meyer, vanished during a trip to the movies where she walked alone. Banker and Gross were found in similar locations outside of Rawlins having died of blows to the head. Four girls were abducted during a 7 week period in a very small town with a low crime rate. Three are closely related and the fourth (Meyer) is probably also related. Long is linked (and is generally assumed to be the perp) only by the fact that he has abducted other young girls in Wyoming, he is suspected of a crime similar to the "rodeo" abductions and, he lived in Rawlins at the time.
If, and only If, Long had ties to Pocatello in July of 1978, I would say he would have to be a strong suspect for Campbell/Anderson; pretty much the same situation as Rawlins.
For the record, Campbell and Anderson were reported to have been seen, at the Pioneer Days celebration, in the company of a young man wearing a blue hoodie and a large ring. Long would have been 43 at the time. A Sheriff involved in the 2008 investigation, reported that his "suspect" was not a Serial Killer. But, his suspect was never charged.
The dump site, particularly if the perp used it for a different victim at a different time, suggests familiarity with the area that someone "just passing through" wouldn't have.
The Bringhurst and Smith abductions were very different from Campbell/Anderson and any of the cases Long is suspected of, but that doesnt rule him out. Serial Killers have been known to change MO's. The one significant difference between Bringhurst and Smith and all of the others is that they appear to have been directly targeted. That still doesn't rule out Long. (Incidentally, Mink Creak, where Bringhursts body was found isnt all that far from the Campbell/Anderson/Jane Doe Dump site; about 25 miles).
All in all, I am not claiming Long is the "Pocatello" killer, only that he needs to be seriously looked at. He was 39 at the time of the Rawlins abductions. How long had he been "moving around" before and after that time? I would think that his movements need to be compared against know murdered or missing girls. He may have far more than he has been given credit for.
P.S. Who is the woman who was bicycling? Are you thinking of Lewiston?