Well that's a more nuanced philosophical discussion for which murder is a poor example. A better one would be something like stealing a candy bar from a grocery

Well that's a more nuanced philosophical discussion for which murder is a poor example. A better one would be something like stealing a candy bar from a grocery store. A found body, or a reported missing person, would yield a response from local law enforcement if the perpetrator could be linked in any way. An example of a stolen candy bar the grocer never noticed missing more directly targets the question of 'if I don't get caught, does it matter'? Anyway, the question here isn't whether you get caught. The question is whether it's actually illegal if there is no copyright holder that anyone knows of, and one doesn't come forward with a legitimate claim. Will law enforcement charge you with a crime? I'm not a lawyer and have no experience with law, but I do love free (and legally so) movies, so I'm genuinely curious about this.