See the second sentence is the problem. That has no bearing on this discussion. If we were careful, moral, and honest, would we have less responsibility for the death there?
If no, why mention it at all? It certainly makes it appear as if, to you, the level of responsibility it somehow dependent upon justice. The two are two completely separate concepts.
If yes, you're being astonishingly clear that you're holding a strange double standard: people are responsible for what they do regardless of how careful, moral, and honest they are. Who would think otherwise, and why?
But it really doesn't matter, you've already admitted to having a double standard anyway, so it's no use having this discussion with you. We're not able to agree on terms. But it's refreshing that you admitted to it.