Rules are formed based on the nature of the actor and the subject under study and arbitrary requirements to achieve a level of certainty the actor desires.
You are arguing from the specific to the general. You have this one airtight case then point at it and ask for agreement to the death penalty. People say no, because the DP more than a single case.
No system can be 100% foolproof, and I think that Crash, et. al. are saying that they will accept nothing less.