[Deathpenalty] death penalty news-----USA

[Rick Halperin]

June 30


USA:

A Death Penalty Puzzle----The Murky Evidence for and Against Deterrence


Although the Supreme Court banned capital punishment for child rape last
week, the justices have made it clear that for homicide, states may
inflict the ultimate penalty. Last month, capital punishment resumed after
a seven-month moratorium. Rapid scheduling of executions followed the
Supreme Court's ruling in Baze v. Rees, reaffirming the constitutionality
of the death penalty in general and lethal injection in particular.

To support their competing conclusions on the legal issue, different
members of the court invoked work by each of us on the deterrent effects
of the death penalty. Unfortunately, they misread the evidence.

Justice John Paul Stevens cited recent research by Wolfers (with co-author
John Donohue) to justify the claim that "there remains no reliable
statistical evidence that capital punishment in fact deters potential
offenders." Justice Antonin Scalia cited a suggestion by Sunstein (with
co-author Adrian Vermeule) that "a significant body of recent evidence"
shows "that capital punishment may well have a deterrent effect, possibly
a quite powerful one."

What does the evidence actually say?

One approach notes that in states with the death penalty, the average
murder rate is about 40 % higher than in states without the death penalty.
Yet such comparisons are surely confounded by other influences, as those
states that impose the death penalty also have a historic culture of
violence, including lynching.

If we compare countries, the United States has higher execution and higher
homicide rates than nearly all other industrialized countries. Here, too,
many alternative explanations remain, making it hazardous to conclude that
the death penalty does not deter murder.

Other studies have evaluated changes in homicide rates over time. In the
1960s, as the death penalty fell into disuse, homicide rates rose sharply,
leading some studies to infer a deterrent effect. Moreover, a large-scale
decline in homicide in the past two decades coincided with renewed use of
the death penalty. Countering this, homicide and execution rates rose
together in the 1920s and early 1930s, then fell together through the
1940s and 1950s. Because conclusions are so sensitive to the time period
evaluated, these studies fail to provide much help.

More sophisticated studies compare the evolution of homicide rates across
jurisdictions. Over the past 6 decades, the homicide rate in Canada has
tracked that in the United States even as the countries' punishment
policies have diverged sharply. Similarly, the 12 states that have not
executed a prisoner since 1960 comprise a useful comparison group; murder
rates in these states have largely tracked those in states that
subsequently adopted or rejected the death penalty.

One might like to conclude that these latter studies demonstrate that the
death penalty does not deter. But this is asking too much of the data. The
number of homicides is so large, and varies so much year to year, that it
is impossible to disentangle the effects of execution policy from other
changes affecting murder rates. Moreover, execution policy doesn't change
often or much. Just as a laboratory scientist with too few experimental
subjects cannot draw strong conclusions, the best we can say is that
homicide rates are not closely associated with capital punishment. On the
basis of existing evidence, it is especially hard to justify claims about
causality.

Justice Stevens argues, "In the absence of such evidence, deterrence
cannot serve as a sufficient penological justification for this uniquely
severe and irrevocable punishment." Perhaps. But the absence of evidence
of deterrence should not be confused with evidence of absence.

Justice Scalia relies on the suggestion by Sunstein and Vermeule that some
evidence suggests a possible deterrent effect. But that suggestion
actually catalyzed Donohue and Wolfers's study of available empirical
evidence. Existing studies contain significant statistical errors, and
slightly different approaches yield widely varying findings, a problem
exacerbated by researchers' tendency to report only those results
supporting their conclusions. This led Sunstein and Vermeule to
acknowledge: "We do not know whether deterrence has been shown. . . . Nor
do we conclude that the evidence of deterrence has reached some threshold
of reliability that permits or requires government action."

In short, the best reading of the accumulated data is that they do not
establish a deterrent effect of the death penalty.

Why is the Supreme Court debating deterrence? A prominent line of
reasoning, endorsed by several justices, holds that if capital punishment
fails to deter crime, it serves no useful purpose and hence is cruel and
unusual, violating the Eighth Amendment. This reasoning tracks public
debate as well. While some favor the death penalty on retributive grounds,
many others (including President Bush) argue that the only sound reason
for capital punishment is to deter murder.

We concur with Scalia that if a strong deterrent effect could be
demonstrated, a plausible argument could be made on behalf of executions.
But what if the evidence is inconclusive?

We are not sure how to answer that question. But as executions resume, the
debates over the death penalty should not be distorted by a
misunderstanding of what the evidence actually shows.

(source: Washington Post; Cass R. Sunstein is the Felix Frankfurter
Professor of Law at Harvard Law School. Justin Wolfers is assistant
professor of business and public policy at the University of
Pennsylvania's Wharton School)