Regarding the blood smudge on the tree:
When I was a toddler, I would spend *hours* looking at the marble tiling of my grandma's bathroom. Eventually I'd start making out characters and scenes, entire story lines of scary beasts and cute animals and armies. One day I ran and got my grandma because I was certain I had seen a goathead that moved and that was terrifying. She scolded me for making up stories, but for me, the fear was 100% real.
We have evolved to make out patterns. Or, rather, our eyes take in bits and bobs of visual data and arrange it in ways that make sense, conjuring familiar shapes and faces.
In a sense, that's what allows us to follow storytelling; most stories, whether it is novels or movies, are based on the Jungian/tragic principles of the hero's journey. Our brain does not like new patterns that we can't identify; they mean chaos. Chaos, to our ancestors, was dangerous. Animals they'd never met before and didn't know if they were venomous. Strange weather patterns that could kill the crops.
There is a great article about how otherwise sane minds can extrapolate logically impossible theories out of data that shouldn't add up.
When the human tendency to detect patterns goes too far | Psyche Ideas
All this to say... it is great to entertain the possibilities, if you are an investigator, early on. Open-mind and the willingness to ask all the questions means you will (ironically) not get tunnel vision on a single POI. But there is a point where it becomes way more prudent to entertain that a smudge on a tree is not an ever-changing rune, but a smudge.
Why?
Because of probability. If you are by a lake and you hear a duck quack, it could, of course, be a drone, playing the recording of a duck quack, and it might mean that there are no more ducks in the world. But if you are actually seeing a duck, visually, that quacks like a duck, and a blood splatter expert says it bleeds like a duck, then it is most likely a duck.
Occam's razor, and all, 100%, my opinion.