The defendant has been recognized by no less than 15 people. His DNA was found all over the crime scene . The victim's blood was found at his clothes. A video recording made by a surveillance camera depicts the whole murder. He himself confessed.

The murder has been staged. Organized crime found a doppelganger, made him wear the victims clothes and kill the other guy on cctv. They contacted the victim and told him to either confess or they will kill his children and parents.

I think society is ok assuming that won’t happen

Yep. That’s what I’m saying. Starting with a required confession is a good start. You could make it as hard as requiring the jury to fail to come up with any other believable narrative.

It’s ok if a criminal can avoid the death penalty by blatantly refusing to confess in light of obviously incriminating evidence.

Confessions are fake all the time, including in many existing "they were executed despite being innocent" cases!

Since we're on completely unrealistic scenarios anyway: that could still be a set up with a false confession.

The real murderer was his long-lost twin, who had previously kidnapped him in a cell, performed the murders and the confession, then snuck out and swapped them!

That’s not a problem with the sentencing

It is. The point is that there can always be more information later. And you can't go back on the death penalty.

I responded to this saying yes, but I think it left too much room for nitpicking. Although I do think this is above the bar, it’s also worth noting that in this scenario, the criminal did in fact seem to leave the crime scene. The much more obvious case is the one where they are caught mid act with many crowd sourced perspectives of the crime, like random shooters.

I actually don't believe that the videos people will use will live up to the standard even if they claim they do. Observing average people, they model probability as a binary 0/1.

They'll look at the video and be like "Yeah he's wearing Carhartt. It's him. He wears it" or whatever. And some other equally clueless nitwit will convince himself it wasn't me because I have 3 blue items and the killer had a red keychain.

Essentially, it is crucial to me to prevent the state from exercising power over me because the agents of the state are frequently morons. And there's nothing worse than morons with power over you since you cannot reason them out of idiocy.

I’m not convinced that you can meaningfully raise the bar beyond “beyond a reasonable doubt” (or even that you can get juries to consistently apply “beyond a reasonable doubt”.)

Regardless of jury instructions, I think what you normally get in practice is “beyond the point at which you are convinced the accused should be treated as guilty”.