There also are a lot of tourists coming to the Christmas markets, sometimes from quite far away.
Those people either completely take public transit (they’ll be drinking anyways, so public transit is easier to get back home) or go for the park + ride offers that pop up during that time. It works pretty well.
I’ve been ruminating on this for a bit (love your other writing btw!) and I think there definitely are good measures of circumstantial evidence that could be used for this!
First - as others have said - preparation for before and after. Butcher tools, different kinds of conservation equipment etc. It wouldn’t exactly fit in a non-anthro situation imo, but there has to be some more natural equivalent, that is probably highly specific to their respective species. What comes to mind first are Shrikes, who impale their prey on sharp thorns or barbed wire. Even having a setup like that close to their living area might be incriminating, and Shrike-specific sub-societies would probably avoid having anything sharp around to begin with just to not seem like they’re up to something.
There definitely would have to be specialists in court that are knowledgeable about predatory behaviors in different species - although, how would you avoid bias, misinformation and just plain ol’ racism? Besides, when your goal is to demonstrate that natural urges can be overcome, it’s a bit counteractive to rely on naturalism just for the case of persecuting the bad guys.
In the same vein, the court could be taking into account whether the victim was of a species that is traditionally seen as prey. A mouse getting preyed on by a cat just sounds a lot more feasible than a cat eating a lion. Although, with Sci-Fi, anything can be possible 🌈 But again, if they’re sentient, the predators would grasp the rules at some point and specifically pick prey that seems unreasonable just in case they get caught.
There could be other common counter indications as well; If the victim is buried for example, or the corpse is disposed of in a way that would make future predation impossible. I imagine that if someone did genuinely commit murder, they’d make sure to drench the victim in acid or some other substance of the sort, just to make sure that they can’t be implicated for predation. Being in possession of such substances for no good reason would make it easy to tell that a murder was premeditated too.
That might not count for species of carrion eaters though. A court could argue that a vulture who buried their victim could still return weeks later and commit predation on the rotten carcass. That again would be a very naturalistic argument for a society that claims to have overcome naturalistic instincts, but it definitely would be interesting to explore as a concept.
You could go a route of psychological plausibility - would a sentient predator really want to see their prey as a person, or would they prefer to mentally unlink and prey on someone they don’t know and can objectify into just being meat? I’d wager the latter would be more common. So if the two involved parties had a history of social interaction, it would make predation less plausible in all but the most fucked up cases. (Those might even involve some messed up form of grooming and social isolation in anticipation of the crime)
Ending on the point of fucked up cases - how would a court deal with a case of a herbivore going specifically against their nature to commit predation? Would the jury be unwilling to prosecute despite overwhelming evidence, just because they’re hung up on it being against natural instincts?
I think you’ve got a very neat system to explore such questions, looking forward to reading more of your writing :)