This week, the death penalty is under fire, as the Supreme Court debates whether or not the death penalty can be applied to convicted murderers with a low IQ, as justices question whether a person can be held accountable for actions that may not be fully understood. It seems an appropriate time to analyze the effectiveness of the death penalty in accomplishing its tasks: reducing the murder rate in the states where it has been applied.
To determine whether the death penalty has acted as an effective deterrent to murder, my Research Methods students Katie Chancellor, Brandon Collins, Dan Garrett, Lauren Jones, Jeremy Maddox, Duncan Parker, Andy Peden, Nick Rawls, Lindsey Weathers, Karly Williams, and John Williamson contributed research to the report. We gathered data on which states have the death penalty, and which do not. We also examined whether both types of states have high or low murder rates, for 2015.
We found that among the 25 states with the highest murder rate, 20 have the death penalty. These include Louisiana, Mississippi, Missouri, South Carolina, Alabama, Delaware, Nevada, Tennessee, Arkansas, Georgia, Oklahoma, Indiana, Florida, North Carolina, Pennsylvania, California, Texas, Kentucky, Virginia and Arizona). Five states (Maryland, Alaska, Illinois, Michigan and New Mexico) also have high murder rates, but not the death penalty.
Among the 25 states with low murder rates, 11 have the death penalty (Kansas, Ohio, South Dakota, Montana, Colorado, Washington, Wyoming, Oregon, Idaho, Utah, New Hampshire). The other 14 states with low murder rates don't have the death penalty. They include Wisconsin, New Jersey, West Virginia, Connecticut, Nebraska, New York, North Dakota, Rhode Island, Minnesota, Iowa, Massachusetts, Maine, Vermont and Hawaii.
For those keeping score, these results are far higher than what an expected model would show. Having the death penalty means you're more likely to be a state with a high murder rate as well, just as states which have eliminated the death penalty are, more likely than not, to have abolished the practice, or never ratified it.
That's not good when you're trying to show that the death penalty deters serious crime.
I challenged my students to think of all kinds of reasons for the results. Some of the more conservative ones challenged the findings. One claimed that perhaps because some states have not executive anyone in a while. Others speculated on why the findings may have turned out the way they did.
This study replicates an earlier study I did with students nearly five years ago. Both showed that the observed cases were significantly different from what's expected from a random model (multiplying the relevant column by the relevant row and divide by the total number of cases). It's the same with this year's study.
Of course, there could be another explanation for the results. States may have the death penalty not as a deterrent, but due in response to higher crime rates (it would be interesting to run a time series model) to see which came first. Or it could be that the electric chair, gas chamber, hanging, firing squad, legal injection, etc. are not to deter crime, but for revenge, or to punish those arrested for breaking the laws on murder in states. Nevertheless, the inability of the death penalty to deter serious crimes should give its supporters some reason to question the effectiveness of capital punishment.
John A. Tures is a professor of political science at LaGrange College in LaGrange, Ga. He can be reached at email@example.com.