1. Self evidence
We can ask ourselves the question: "would I give up my right to life in order to take it away from all others". The answer to this question is always no. This establishes the self evidence of the right, regardless of any governmental authority.
2. The experiment is expanded to N=20 and beyond.
We can ask any number of groups of people (with like power) this question. Every individual will answer the same as we did. This establishes, as a matter of scientific experiment, that the right to life is a natural right and not dependent upon government authority.
3. We must understand that inalienable does not equal inviolable.
A right can be violated (both justly and unjustly). This does not make the right cease to exist. Just because someone is murdered does not mean they had no right to life; clearly, they had a right to life and it was violated.
When we speak of inalienable, we are referring to the universality of natural rights among people and not an imagined inviolability of any right.
4. We must grasp that this experiment and the understanding that comes with it is the basis of the US Constitution.
If we understand the concept of natural rights, then we understand the revolutionary nature of the government created by the founders. Only through this understanding can the Constitution be interpreted rationally.
Natural rights are socially natural objects. The arise in every like-powered group of people and they always will.