The Supreme Court has been aware of racial disparities like these for a long time. In a case decided in 1987, the justices were presented with a study finding that people accused of killing white victims in Georgia were four times as likely to be sentenced to death as those accused of killing black victims. But the court, in a 5-to-4 opinion by Justice Lewis Powell, said that given the many procedural safeguards in capital trials, the study “does not demonstrate a constitutionally significant risk of racial bias.” (After retiring, Justice Powell said he should have voted the other way.)

The new report shows that Louisiana’s death penalty isn’t only consistently racist; it’s also profoundly error-prone. Of the 155 death sentences the state has handed down and resolved since 1976, 28 resulted in executions. The other 127 — or 82 percent — were later reversed. Since 2001, two people have been executed, while 53 have had their death sentences reversed.

These reversals are usually the result of major errors at trial that violate the defendant’s constitutional rights, such as prosecutorial misconduct, improper jury instructions and incompetent lawyering. In most cases, the discovery of these errors resulted in the defendants’ being removed from death row and receiving lesser sentences. In nine of the cases, though, the defendant was fully exonerated of the crime and cleared of all charges.

Louisiana’s record is terrifying, but other capital punishment states aren’t much better. Nationwide, the reversal rate for resolved death sentences is 72 percent, and while the average exoneration rate for death row inmates in other states is 1.8 percent (less than half of Louisiana’s rate), that still translates to a national total of 156 innocent people sentenced to death and later exonerated since 1973.