It’s most definitely a fallacy. It puts forth a conclusion without sufficient evidence to justify the conclusion. Just like an argument from authority or a gambler’s fallacy.
It’s not actually putting it forth as a conclusion though—it’s just a flaw in our wetware that makes us interpret it as such. We could imagine a perfectly rational being who could accurately work out the probability of a particular person having done it, then randomly sample the population (or even work through each one in turn) looking for the killer. Our problem as humans is that once the idea is planted, we overreact to confirming evidence.
It’s most definitely a fallacy. It puts forth a conclusion without sufficient evidence to justify the conclusion. Just like an argument from authority or a gambler’s fallacy.
It’s not actually putting it forth as a conclusion though—it’s just a flaw in our wetware that makes us interpret it as such. We could imagine a perfectly rational being who could accurately work out the probability of a particular person having done it, then randomly sample the population (or even work through each one in turn) looking for the killer. Our problem as humans is that once the idea is planted, we overreact to confirming evidence.