Arbitrary, capricious, immoral. America’s death penalty is all of those things. Finally, a politician has had the guts to stand up and say so and do something about it.

Former Illinois Gov. George Ryan is catching a lot of heat from a lot of camps — cops, prosecutors, the families of victims — for having commuted the sentences of 167 inmates to life in prison. There were 156 inmates on death row, with the rest awaiting sentencing on capital murder cases. Now, all but three of the death-row inmates face life in prison without parole.

Ryan, whose term ended last Monday, didn’t go into the death-penalty issue with his eyes closed. It’s death-penalty proponents who refuse to see the reality. Years of studies have exposed a broken system, what Ryan called “the demon of error” in our system of justice.

From Florida to California to all points in between, the death penalty is riddled with mistakes and manipulations that impose little fairness or uniformity for the accused. Black people and the poor are more likely to get the death penalty than those who have the money to pay the best defense lawyers to bargain for a life sentence or better.

“Because the Illinois death-penalty system is arbitrary and capricious, and therefore immoral, I no longer shall tinker with the machinery of death,” Ryan said Saturday. Ryan’s years in office haven’t been without scandal, but those issues should not be confused with the courageous stand he took on the death penalty. Justice demanded he act.

Mistakes made by police in gathering evidence, by the coroner’s office examining bodies, by the prosecutors refusing to go after evidence that would exonerate an accused murderer. All of that and more pointed to the injustice of the current system.

Because it’s not just about the differences in race in sentencing. Similar killings brought very different sentences from county to county, Ryan pointed out. “Forty years in one county and death in another,” he noted.

Ryan, a Republican, made the news three years ago when he put a moratorium on all executions in his state after courts found that 13 men had been wrongly convicted since Illinois reinstated the death penalty in 1977.

Science has helped make the case against the death penalty even more powerful. DNA testing has exposed wrong convictions galore in many states.

Ryan also pardoned four other men on death row because it had been proved beyond any reasonable doubt that police had tortured those men to confess to crimes they never committed. One remains in prison for another crime.

To do away with the death penalty does not mean quashing justice. People who kill others must be punished. A life sentence without parole for murder is no free ride. It is a civilized society’s way of saying that we won’t stoop to a murderer’s level, but we will protect innocents from killers imprisoned until they die as their maker sees fit. Justice done.