It is speculation but there is pretty good circumstantial evidence.  We are not in court and we will not be able to get the kind of hard evidence you might want. So we have to use logic and observation and form opinions on circumstantial evidence and probabilities. Hillary's New York city address was really a fancy medical facility. Radical gene therapy of some kind or even cloning is not an absurdity, and the hard medical evidence will be hidden behind a wall of privacy.