The deterrence element of punishment is often overstated. Punishment is a really poor behavioral modifier. For punishment to reliably modify behavior, it has to

The deterrence element of punishment is often overstated. Punishment is a really poor behavioral modifier. For punishment to reliably modify behavior, it has to be immediate and consistent. The criminal justice system is neither. It is not only behavioral scientists that are aware of the flaws, criminologists also look at the data, and there seems to be no indication that the severity of the punishment is negatively correlated with the frequency of the crime, neither across time, nor between jurisdictions with different penal code. What criminologists have found however is that racial minorities are often given the harsher punishment when available (the reason WA deemed the death penalty unconstitutional back in 2018; and they had the data to back it up). So the deterrence value seems to be primarily used to discriminate against minorities, not to reduce crime rate.