Challenges:
* Y-san says poison was ingested, so no accidental seppuku
* Violet says nobody could get near Victor or his mise en place, so no poisoning his food or equipment.
* B-kun the Infallible says that any of the partners could be implicated by the A, (and so could Violet, although more ambiguously), so therefore we can't tell who did it from the letter
* B-kun says that the murderer probably removed the poisoned evidence.
* Most of us are suspicious of Violet's manner when describing the murder scene, but Y-san rejects that kind of reasoning because it's really about the trickiness of the culprit.
Other data:
* Violet says the police learned that the three partners each had visited the kitchen, coming out with specific items. Perhaps we can actually believe her, and believe that she did NOT enter the kitchen until she found the body.