A July 18 CNSNews.com article by Kevin Mooney examined the possibility of New Jersey repealing the death penalty "in the face of academic studies challenging the view that the death penalty is not an effective deterrent to murder." Mooney cited a number of studies that claim a state-enforced death penalty prevents murders, as well a study that claims the opposite, but he bolstered the claims of the former studies and denigrated the claims of the latter.
Mooney specifically cited two studies by Emory University researchers, as well as a study by University of Colorado researchers, claiming that the death penalty has a deterrent effect. He featured the first Emory study at length, which claimed "that there are an average of 18 fewer murders for every execution," quoting one of the study's researchers. Mooney also featured Michael Rushford of the Criminal Justice Legal Foundation, which favors the death penalty, calling these studies noteworthy because they come from economists "who have no political axe to grind."
Mooney also stated that "death penalty opponents cited another study, released last year in the Stanford Law Review, that directly challenging the findings in the Emory study and similar reports." But rather than bolstering the academic credentials of its researchers, Mooney quotes one of the authors of the Emory study calling it "a serious but flawed critique" and that "his team is preparing a rejoinder to the Stanford Law Review study."
Such selective reporting suggests that the Emory studies have never been seriously questioned on an academic level, which is false. As Casey Stubbs at the Huffington Post details:
John Donohue, Yale Law School professor and Research Associate at the National Bureau of Economic Research, and Justin Wolfers, Wharton School of Business professor and Research Affiliate at the NBER, analyzed the same data used in the Emory and Denver studies, as well as other studies by the same researchers and many other nationwide reports. They found that if anything, executions increase homicides, concluding: "The view that the death penalty deters is still the product of belief, not evidence ... On balance, the evidence suggests that the death penalty may increase the murder rate."
Donohue and Wolfers analyzed data from the 2006 study by the Emory researchers using non-death penalty states as a control group, a basic statistical tool used to study causation not used in the Emory study. When they compared death penalty states with non-death penalty states, they found no evidence of any effect of executions on murder rates, either up or down. Donohue and Wolfers also analyzed the data from the 2003 Emory study that concluded that each execution prevented 18 murders and found that the reduction or increase in murders was actually more dependent on other factors used in the study than whether or not the states had the death penalty. For example, when Donohue and Wolfers slightly redefined just one of the factors included by the Emory researchers, they found that each execution caused 18 murders.
Donohue and Wolfers also recomputed data from the Denver study of select states to account for overall crime trends, a factor not included in the Denver study, and reached inconclusive results. For two states included in the Denver study that had abolished the death penalty, Massachusetts and Rhode Island, Donohue and Wolfers found that the homicides rates actually fell after capital punishment was ended.
There's a lot more death penalty research going on than Mooney suggests -- and, also, more questioning of the "deterrent effect" than he wants his readers to know.