That's a fair assessment to suggest that life in prison is better than a death sentence. I'll agree with that.
However, like I said before, there are cases that can be 100% true. Some cases are based on circumstantial evidence which places conviction on a probability. Those cases that are 100 percent can be allowed maximum punishment including capital punishment.
I'll just add an example of cases that can be 100% true.
There is no doubt who the shooter in the parkland massacre was and what was done. I don't need to mention names.
We can safely convict him and punish him to the extent of the law.