It doesn't matter who believes what, Japan's court system is not a TV drama like in the US. It's not about convincing anyone with theatrics and the jury does not give final ruling. There's either enough evidence to link her to the murder beyond reasonable doubt, or there isn't. In this case there's zilch, all conjecture like in the previous incidents. As in all other chapters, the culprit only goes down because they admit it themselves. The author really isn't bright enough to come up with a quality intrigue.