I agree with Moriarty-kun. Even if it is his blood, these wounds reopen regularly - there may be some convoluted means that was used to extract the blood from him at an earlier time and plant it now. I can't quite tell why the culprit would have bled. Did he demand Momota-kun duel him to the death with a sword, is that why there are two?

[Makima turns from Alastor to Moriarty, her hair swishing over her shoulder.]

Though... Moriarty-kun has a flair for the dramatic, the self-sacrificing, and drawing out information from others, as a culprit aware of the presence of a double agent might want to do. The "dead man's hand" had the desirable paired cards. Perhaps the winner of the fight is nevertheless a dead man.

I just thought that was interesting. I'll get back to my analysis soon.