I think persons stop being persons the moment they die in most countries. However, I expect that the moment it becomes common knowledge or they tell you upfron

I think persons stop being persons the moment they die in most countries. However, I expect that the moment it becomes common knowledge or they tell you upfront about it, courts would rule living people who consider donating their body to science would be discriminated against. Given that, I would think keeping it 100% a secret wouldn’t work, either, as keeping crimes/misdemeanors secret never makes them legal.