Just posting this as an addendum to the information from the comment above. There is a 3D printed device called a Sarco Pod that has been developed for assisted suicides. As far as I know, it has yet to be deployed. However, it seems likely that it will be in the near future.

The prevailing objections to the death penalty appear to stem from the nature of the methods that have been utilized. I wonder if the sentiment would change if receiving the death penalty was effectively painless, and nearly instantaneous via one of these pods?

At that point you could certainly make an argument for life in prison being a significantly harsher, elongated, and cruel sentence. Just some food for thought.

https://en.m.wikipedia.org/wiki/Sarco_pod