I can tell you what I know about these two postmortem changes...full disclosure, I haven't seen any part of the coroner's report.
Lividity is, as
@crush stated, the gravitational pooling of blood in the body after death. It starts occurring pretty much as soon as blood circulation ceases. It's a dark reddish purple coloration of the skin that's usually fully evident after about 3-4 hours and fixed after 8-12 hours. I think a lot of people here probably know about rigor mortis, the stiffening of the body after death and how rigor mortis eventually goes away? Livor mortis, or lividity, doesn't go away after it's fixed and even moving the body position will not cause it to disappear after that point.
Lividity is evident not only on the skin but also in the internal organs. So even if injury to the skin or other factors made it hard to see externally, internal examination would reveal it.
The physiological mechanism that causes lividity can be pretty variable among individuals so just by itself, it can't be used to yield an exact time of death.
I only know of one thing that can "prevent" lividity from forming and that would be a severely anemic body. Outside of that, some type of lividity would have been present in Braylen IMO. As stated above, it can't go away once it is fixed and that happens relatively soon after death.
Marbling, also as
@crush stated, is part of the decomposition process. It is entirely unrelated to body position after death. After death, intestinal bacteria and other microorganisms spread throughout the body. One of these pathways is along blood vessels. As they proliferate, they turn adjacent body tissues green, red and black. When this occurs in veins just under the skin, this artifact is called marbling.
In bodies after death, decomposition processes occur at different rates in different parts of the body, and this can vary from person to person. So I don't read too much into the fact that marbling was seen on his chest and face but not mentioned in other body parts. What we can take away from this is that Braylen wasn't recently killed (within a few hours or a day of) when he was found in the pool. Marbling as part of the decomposition process is not one of the very first changes to occur after death.
All MOO.[/QUOTE