You can actually download the 300-page report commissioned by the Wolf administration studying factors related to the death penalty. A diverse team of experts spent three years on it and found 16 categories of reasons to not execute anyone. Besides innocent people being executed, widespread lying by cops, systemic racism, and flawed technology, execution costs many times more money than life imprisonment. We also know that "general deterrent" is a myth. There is no moral, ethical, civil, or financial reason to execute.