in the last 50 years in the US 190 former death-row prisoners have been exonerated of all charges related to the wrongful convictions that had put them on death row, a pretty strong argument against the death penalty.
Then there's this from a NY Times article: Black lives do not matter nearly as much as white ones when it comes to the death penalty, a new study has found. Building on data at the heart of a landmark 1987 Supreme Court decision, the study concluded that defendants convicted of killing white victims were executed at a rate 17 times greater than those convicted of killing Black victims.