[... Karl has to wonder who ever said that, because now that he's in the position of being a hypothetical/falsely accused criminal, he's not quite sure how it'd be true. Then again, maybe he just doesn't think like one.]

Sorry, but I'm not in the habit of confessing to crimes I didn't commit.

[...]

Not to mention that I'd rather we find the real murderer, and taking the blame for this is only going to hurt that. On what grounds are you even accusing me of being the one who did it, anyway?

[He doubts any of this is seriously going to change this guy's mind, but still, he'll say it as he believes it.]