We don't know when they started that day. That they started very late, is just someone's guess that has unfortunately been copied all over the web as fact.
That is true - we don't really know when they started. However, from their photos taken on 1. February morning it seems that there was a full daylight, but their tent was still standing, they were not yet packed and ready. They probably still had to do the "Labaz" that morning (if the "labaz" was really made by them). So I think it is quite possible that they started late. But what happened next - why did they pitch the tent on the slope in bad weather (assuming from the photos) is a mystery. They could have descended to the forest (cedar area, on their original route!) where there was wood, trees for pitching the tent, no strong wind.. but they decided to stay on the slope.
Regarding the "murder" theory - I think that instead of speculating about the motive, bodies disposal etc., we should stick to the facts and evidence available in the autopsy reports and post-mortem photos.
My assumption that they were murdered (or at least some of them) is based on these points:
- all of them except of Doroshenko and Dyatlov had injuries on the side of their head (open wounds, fractures, in case of Slobodin on both sides). Dyatlov is disputable - there is a head wound visible through his hair on one of the morgue photos.
- many of them had severe face damage - swollen and bleeding lips, bleeding nose, multiple bruises and abrasions on their cheeks etc. Dyatlov had identical bruises on both of his cheeks (morgue photo). It is difficult to believe that symmetrical head injuries of Dyatlov and especially Slobodin would happen by accident. In Slobodin's case, he would probably be unconscious even after the first head fracture. How did he get the second one (which would make him unconscious too)? There was nothing near the place where he was found to cause these fractures.
- Injuries omitted or not described properly in the autopsy reports: missing histology results, vague statements about deformed neck (Kolevatov..), Zolotaryov's shoulder bone fracture not described by the pathologist but found after he was exhumed..
- Many of them found in unnatural positions: Doroshenko, Krivonishenko, Dyatlov. They were moved after their death, and in case of Doroshenko it was some time after the death, as livor mortis has already formed on the other side of his body (suggests that he was turned). Krivo's trousers were probably arranged to cover his foot, which was severely burned from below. Traces of blood on his leg indicate that he was in vertical position when he got injuries in the area of his upper thigh (so the injuries were not caused by cutting his trousers after he was dead).
- Probable presence of other people in the cedar area and also in the tent: army putees, spoon. From the "den" photo it seems that the spruce/fir branches for the flooring were cut by one single blow (axe), not with a knife.
So to me, murder is the most probable cause of the death of most of the group. Also, from their behavior and various hints (clothing, gloves etc.) it seems that they did not act together but were divided into two or more groups - but this is for another discussion:).