True, which is what a notary is for. You could encrypt the data to be leaked at a notary, with the private key split using shamir's shared secret among your beloved ones (usually relatives). If all agree, they can review and decide to release the whistleblower's data.

This statement confused me, but according to Wikipedia the job description of a notary is different in different parts of the world. If you live in a “common law” system (IE at one point it was part of the British Empire), it is unlikely that a notary would do anything like what you are saying.