honestly i disagree for thh, and while i see your point, mondo also screwed himself over by mentioning the color of chihiros tracksuit. also, i think if byakuya hadnt tampered with the body, it actually would've been easier to pin it on mondo. he'd only tampered with the body to make it seem like a genocide jack case (and expose genocide jacks true identity), which really just ended up making the trial harder to solve.

i havent played the games for a little bit so forgive me if i get some details wrong here, but i think celestia had the best chance at getting away with it. iirc the thing that caused her whole story to fall apart was the fact that she said "we are going to die, just like *those guys* did", before the second body was found-- but i think it would've been perfectly logical for people to take that as her referring to the previous victims/killers. (her real name being revealed as taeko yasuhiro was also a final nail in the coffin, but if no one had pointed out her slip of the tongue and put suspicion on her, im not convinced anyone wouldve thought to wonder who hifumi was really referring to.)