In my opinion there is nothing to the owl shirt. Coincidence. What possible purpose could the choice of shirt had in relation to the conspiracy? How could it have served as some kind of “signal” to the killer(s) if they never saw it?
How would Luis/Sig/Katie have known, in advance, that there would be an owl, in a particular tree, right near where they were located, at a particular time, such that Luis could photograph it? (They wouldn’t.) And why would he say that Katie got angry that he did that and told him to take it down?
The reason the drive-by, for example, might be less easy to dismiss as a coincidence is because criminals do sometimes drive by the scene, and because Wendi has had several different explanations for it. It seems to have raised suspicions, and there could be a possible crime-related explanation for it (she couldn’t help herself.)
By contrast, with the owl, the alleged crime-related explanations some people cite for it to me make no sense, as I explain above. Also, criminals aren’t known to use t-shirt codes, or take pictures of wildlife. Indeed, if the owl had not been in that tree, the crime could still have occurred, and Wendi still might have worn that shirt. The cops did not ask her about her shirt that day, the state has never asked her about it, and if they didn’t find it suspicious, neither do I.