@elbow well, his daughter probably object and plead for guilty if he actually sued dr Koto.
But it's still can't be proved regardless. You need medical records and a prove that you've been given medication of the misdiagnosed disease. (Oh and yeah, political power may affect it too) every disease have differential diagnosis, and time is also a crucial factors too. Assumption is not always correct, that's why doctors need additional examination like x-ray and etc before making an actual diagnosis.
I know I'm not a lawyer, but I'm studying on medical degree right now so I know a little bit. It may vary by the country tho.