The same statistics which come up every time also come up in Ohio: if you kill a white person you are more likely to get the death penalty than if you kill a black person. This has raised the usual calls for a moratorium.
This argument does raise the bias issue. The problem is that those who oppose the death penalty don't seem to realize that it doesn't help their argument.
I'm not a statistician, so I'll assume that every single other factor (such as the class of the victim, class of the accused, or locality) has been eliminated and the only element involved is race (a la the Baldus study) . "Death sentences were handed down in 18 percent of cases where the victims were white, compared with 8.5 percent of cases where victims were black."
If you're not outraged - or at the very least bothered - by that something's wrong with you. Those percentages show that the life of a murdered Black citizen is valued less than the life of a murdered White citizen.
But this is also the problem with making the anti-death penalty argument using these statistics. Those statistics call for an equalization in value. The argument that they should lead to fewer death penalty cases is an argument that the life of White citizens must be devalued. Some may make this argument but it's not a winner. It runs counter to the moral current to argue that a group of people must be devalued.
On the other hand, these statistics clearly point to a need to make our institutions (in particular our prosecutors) raise their valuation of the life of slain Black citizens. This requires that more people accused of killing Black citizens be subjected to the death penalty.
Nor is it a solid argument for abolishment of the death penalty. If memory serves me, it was Justice O'Connor who toyed with the anti-death penalty advocate in McCleskey v. Kemp by pointing out that his argument was a strong point in favor of taking discretion away from the prosecutors and requiring a death penalty prosecution for every single case which fell within certain parameters. And it is. The primary flaw in the system seems to be the prosecutors not pursuing cases evenly. If every single case which had more than one victim required a death penalty prosecution (as an example) it would solve this problem and all prosecutions would be based upon factors clearly not related to race.
Please find a better argument. This one only works for the true believers. They're not the ones who need convincing.