The horses of Skyrim are one of the game's most memetic elements, but they also introduce a massive plot hole into the game. The game's bounty system includes horses as witnesses, which makes absolutely no sense, seeing as how horses in Skyrim cannot talk, and thus cannot report the crime. As such, they cannot be counted as witnesses to the crime being committed.
Skyrim has a lot of systems in place to keep track of the player's actions in the world, both helpful and hurtful, as well as how the world responds to said actions. The most prominent of these systems, used in every town, is the bounty system in Skyrim, which covers the player's crimes and how much money is put on their wanted posters. The bounty amount is determined in part by how many NPCs are witness to the player's actions.
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For the most part, this system works very well. It encourages players to think before committing any crimes, since NPCs are everywhere, even in smaller towns, and are quick to point out when someone is doing something they shouldn't. However, not everyone who sees the player committing a crime is necessarily in a position to tell anyone about it. Case in point, for some reason, horses count as witnesses in Skyrim.
Lots of people play Skyrim wrong, and sometimes intentionally, so it's no surprise that a lot of people get caught when trying to do something that breaks the law. But to have the bounty go up if a horse sees the player doing something is just absolutely absurd. This is only an occurrence when the player steals a horse from someone's stable. The bounty goes up based on the apparent testimony of both the horse the player stole as well as any other horses
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