Exactly. If you kill someone in front of two surviving witnesses and it is caught on a well-lit good definition video, sure, that's beyond any reasonable doubt, execute away.
Short of that? Nah, let's err on the side of caution and not go around executing potentially innocent people, please.
What if the two witnesses were lying? What if the video was deepfaked? Plenty of executions and imprisonments from a few decades ago that were judged "beyond any reasonable doubt" at the time were found to be wrong as soon as DNA testing became a thing, and the racial and other kinds of bias in the justice system became immediately clear. What is the guarantee that the same thing won't happen for any executions done today?
