Dearth of Good Death Penalty Data

Deterrent effect? The lethal injection room at San Quentin State Prison in California.

It's a staple of debate over criminal justice in the United States: Does the death penalty deter homicide?

There's no way to know, according to a new study from the National Research Council. Studies conducted since a brief moratorium on the death penalty ended in 1976 "do not provide evidence for or against the proposition that the death penalty affects homicide rates," the study concludes.

"Fundamental flaws in the research we reviewed make it of no use in answering the question of whether the death penalty affects homicide rates," said Daniel S. Nagin, a public policy scholar at Carnegie Mellon University in Pittsburgh, Pennsylvania, and chair of the committee that wrote the report. "We recognize that this conclusion may be controversial to some, but no one is well-served by unsupportable claims about the effect of the death penalty, regardless of whether the claim is that the death penalty deters homicides, has no effect on homicide rates or actually increases homicides."

Read more about the report.