|
||||||||||||||||
|
||||||||||||||||
|
|
|||||||||||||||
|
| ||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 9
1
Introduction
I
n 1976 the Supreme Court decision Gregg v. Georgia (428 U.S. 153)
ended the 4-year moratorium on executions that had resulted from its
1972 decision in Furman v. Georgia (408 U.S. 238). In Furman the
Court had ruled that the death penalty, as then administered in the United
States, constituted cruel and unusual punishment in violation of the Eighth
Amendment to the Constitution. Then, in Gregg, it had ruled that the death
penalty is not, in all circumstances, cruel and unusual punishment, thereby
opening the way for states to revise their capital punishment statutes to
conform to the requirements of Gregg.
In the immediate aftermath of Gregg, a National Research Council
report reviewed the evidence relating to the deterrent effect of the death
penalty that had been published through the mid-1970s. That review was
highly critical of the available research, concluding (1978, p. 9):
The flaws in the earlier analyses finding no effect and the sensitivity of
the more recent analysis to minor variations in model specification and
the serious temporal instability of the results lead the panel to conclude
that available studies provide no useful evidence on the deterrent effect of
capital punishment.
THE CURRENT DEBATE
During the 35 years since Gregg, and particularly in the past decade,
many studies have renewed the attempt to estimate the effect of capital
punishment on homicide rates. Most researchers have used post-Gregg
data from the United States to examine the statistical association between
9
OCR for page 10
10 DETERRENCE AND THE DEATH PENALTY
homicide rates and the legal status or the actual implementation of the
death penalty.
The studies have reached widely varying, even contradictory, conclu-
sions, and commentary on the findings has sometimes been acrimonious.
Some researchers have concluded that deterrent effects are large and robust
across datasets and model specifications. For example, Dezhbakhsh, Rubin,
and Shepherd (2003, p. 344) concluded that:
Our results suggest that capital punishment has a strong deterrent effect;
each execution results, on average, in eighteen fewer murders with a mar-
gin of error of plus or minus ten. Tests show that results are not driven by
tougher sentencing laws and are robust to many alternative specifications.
Similarly, Mocan and Gittings (2003, p. 453) stated the following:
The results show that each additional execution decreases homicides by
about five, and each additional commutation increases homicides by the
same amount, while an additional removal from death row generates one
additional murder.
In 2004 testimony before Congress, Shepherd (2004, p. 1) summarized this
line of evidence on the deterrent effect of capital punishment as follows:
Recent research on the relationship between capital punishment and crime
has created a strong consensus among economists that capital punishment
deters crime.
However, the claims that the evidence shows a substantial deterrent
effect have been vigorously challenged. Kovandzic, Vieraitis, and Boots
(2009, p. 803) concluded that:
Employing well-known econometric procedures for panel data analysis,
our results provide no empirical support for the argument that the exis-
tence or application of the death penalty deters prospective offenders from
committing homicide . . . policymakers should refrain from justifying its
use by claiming that it is a deterrent to homicide and should consider less
costly, more effective ways of addressing crime.
Others do not go so far as to claim that there is no deterrent effect, but
instead argue that the findings supporting a deterrent effect are fragile, not
robust. Donohue and Wolfers (2005, p. 794) reanalyzed several of the data
sets used by the authors who claimed to have found robust deterrent effects
and concluded that:
We find that the existing evidence for deterrence is surprisingly fragile,
and even small changes in specifications yield dramatically different re-
OCR for page 11
11
INTRODUCTION
sults. Our key insight is that the death penalty—at least as it has been
implemented in the United States since Gregg ended the moratorium
on executions—is applied so rarely that the number of homicides it can
plausibly have caused or deterred cannot be reliably disentangled from the
large year-to year changes in the homicide rate caused by other factors.
Berk (2005, p. 328) reached a similar conclusion:
. . . the results raise serious questions about whether anything useful about
the deterrent value of the death penalty can ever be learned from an obser-
vational study with the data that are likely to be available.
Not surprisingly, the criticisms of the research claiming to have found
deterrent effects have generated defenses of the research findings and the
methodologies used, as well as counterclaims about the deficiencies in
the methods used by the critics. For instance, in response to the Kovandzic,
Vieraitis, and Boots (2009) claim of no deterrent effect, Rubin (2009,
p. 858) argued that:
the weight of the evidence as well as the theoretical predictions both argue
for deterrence, and econometrically flawed studies such as this article are
insufficient to overthrow this presumption.
In response to Donohue and Wolfers (2005, 2009), Zimmerman (2009,
p. 396) argued that:
This paper shows that many of D&W’s [Donohue and Wolfers] criticisms
of Zimmerman’s original work do not hold up under scrutiny, and other
authors have also rebutted D&W’s criticisms of their research.
Beyond disagreement about whether the research evidence shows a
deterrent effect of capital punishment, some researchers claim to have
found a brutalization effect from state-sanctioned executions such that
capital punishment actually increases homicide rates (see, e.g., Cochran and
Chamlin, 2000; Thomson, 1999). Evidence in support of a brutalization
effect is mostly the work of sociologists, but it is notable that in her latter
work Shepherd also concluded that brutalization effects may be present
(Shepherd, 2005).
COMMITTEE CHARGE AND SCOPE OF WORK
The Committee on Deterrence and the Death Penalty was organized
against this backdrop of conflicting claims about the effect of capital pun-
ishment on homicide rates, with the following charge:
OCR for page 12
12 DETERRENCE AND THE DEATH PENALTY
This study will assess the evidence on the deterrent effect of the death
penalty—whether the threat of execution prevents homicides. The focus
will be on studies completed since an earlier National Research Council
assessment (National Research Council, 1978). A major objective of this
study is to evaluate underlying reasons for the differing conclusions in
more recent empirical studies about the effects of the legal status and ac-
tual practice of the death penalty on criminal homicide rates. The commit-
tee will develop a report about what can be concluded from these studies
and also draw conclusions about the potential for future work to improve
upon the quality of existing evidence.
Issues and questions to be examined include the following:
1. Does the available evidence provide a reasonable basis for drawing
conclusions about the magnitude of capital punishment’s effect on
homicide rates?
2. Are there differences among the extant analyses that provide a ba-
sis for resolving the differences in findings? Are the differences in
findings due to inherent limitations in the data? Are there existing
statistical methods and/or theoretical perspectives that have yet to
be applied that can better address the deterrence question? Are the
limitations of existing evidence reflective of a lack of information
about the social, economic, and political underpinnings of homi-
cide rates and/or the administration of capital punishment that first
must be resolved before the deterrent effect of capital punishment
can be determined?
3. Do potential remedies to shortcomings in the evidence on the de-
terrent effect of capital punishment have broader applicability for
research on the deterrent effect of noncapital sanctions?
In addressing those questions, we focused on the studies that have been
undertaken since the earlier assessment (National Research Council, 1978).
That assessment has stood largely unchallenged: none of the recent work,
whatever its conclusion regarding deterrence, relies on the earlier studies
criticized in that report or attempts to rehabilitate the value of those studies.
It is important to make clear what is not in the committee’s charge.
Deterrence is but one of many considerations relevant to deciding whether
the death penalty is good public policy. Not all supporters of capital pun-
ishment base their argument on deterrent effects, and not all opponents
would be affected by persuasive evidence of such effects. The case for
capital punishment is sometimes based on normative retributive arguments
that the death penalty is the only appropriate and proportional response
to especially heinous crimes; the case against it is sometimes based on
OCR for page 13
13
INTRODUCTION
similarly normative claims that the sanctity of human life precludes state-
sanctioned killings, regardless of any possible social benefits of capital
punishment. Separate from normative considerations, deterrence is not the
only empirical issue relevant to the debate over capital punishment. Other
considerations include whether capital punishment can be administered in
a nondiscriminatory and consistent fashion, whether the risk of a mistaken
execution of an innocent person is acceptably small, and the cost of admin-
istering the death penalty in comparison with other sanction alternatives.
Although there is empirical evidence on the issues of discrimination,
mistakes, and cost, the charge to the committee does not include these
questions. Nor have we been charged with rendering an overall judgment
on whether capital punishment is good public policy. We have been tasked
only with assessing the scientific quality of the post-Gregg evidence on the
deterrent effect of capital punishment and making recommendations for
improving the scientific quality and policy relevance of future research.
In including recommendations for future research, the study’s statement
of task recognized that potential remedies to shortcomings in the evidence
on the deterrent effect of capital punishment on homicide might also be
used in the study of the crime prevention effects of noncapital sanctions.
Thus, this report also offers recommendations for improving the scientific
quality and policy relevance of that research.
The post-Gregg studies can be divided into two types on the basis of
the type of data analyzed. Panel data studies analyze sets of states or coun-
ties measured over time, usually from about 1970 to 2000. These studies
relate homicide rates over time and the jurisdictions covered to the legal
status of capital punishment or the frequency of executions or both. Time-
series studies generally cover only a single geographic unit, which may be
as large as a nation or as small as a city. These studies usually examine
whether there are short-term changes in homicide rates in that geographic
unit in the aftermath of an execution. We review and critique these two
types of studies separately because their design and statistical methods are
quite different.
Assessing the deterrent effect of the death penalty is much more than
a question of interest to social science research. It is a matter of importance
to U.S. society at large, and we expect that a potentially broad audience
will want to understand how the committee reached its conclusions. Yet
the research that the committee has had to appraise is a body of formal
empirical work that makes use of highly technical concepts and techniques.
The committee has been mindful of the importance of reaching as broad an
audience as possible while meeting the fundamental requirement that the
report be scientifically grounded. With this in mind, Chapters 1, 2, and
3 (as well as the summary) have been written for a broad, largely policy
audience, largely avoiding technical language. In contrast, Chapters 4 and
OCR for page 14
14 DETERRENCE AND THE DEATH PENALTY
5 include some exposition and analyses that are aimed for the researchers
in the field.
Chapter 2 summarizes homicide rates and the legal status and practice
of execution in the United States from 1950 to the present. Chapter 3 pro-
vides an overview of the possible mechanisms by which the legal status and
practice of execution might affect homicide rates and also provides a non-
technical primer on some of the key challenges to making valid inferences
about the deterrent effect of the death penalty. Chapters 4 and 5 review and
assess the panel and time-series studies, respectively. Chapter 6 elaborates
on the theoretical and statistical challenges to drawing valid conclusions
about the deterrent effect of the death penalty, and presents our conclusions
and recommendations for future research.
REFERENCES
Berk, R. (2005). New claims about executions and general deterrence: Déjà vu all over again?
Journal of Empirical Legal Studies, 2(2), 303-330.
Cochran, J.K., and Chamlin, M.B. (2000). Deterrence and brutalization: The dual effects of
executions. Justice Quarterly, 17(4), 685-706.
Dezhbakhsh, H., Rubin, P.H., and Shepherd, J.M. (2003). Does capital punishment have a
deterrent effect? New evidence from postmoratorium panel data. American Law and
Economics Review, 5(2), 344-376.
Donohue, J.J., and Wolfers, J. (2005). Uses and abuses of empirical evidence in the death
penalty debate. Stanford Law Review, 58(3), 791-845.
Donohue, J.J., and Wolfers, J. (2009). Estimating the impact of the death penalty on murder.
American Law and Economics Review, 11(2), 249-309.
Kovandzic, T.V., Vieraitis, L.M., and Boots, D.P. (2009). Does the death penalty save lives?
Criminology & Public Policy, 8(4), 803-843.
Mocan, H.N., and Gittings, R.K. (2003). Getting off death row: Commuted sentences and the
deterrent effect of capital punishment. Journal of Law & Economics, 46(2), 453-478.
National Research Council. (1978). Deterrence and Incapacitation: Estimating the Effects of
Criminal Sanctions on Crime Rates. Panel on Research on Deterrent and Incapacitative
Effects, A. Blumstein, J. Cohen, and D. Nagin (Eds.). Committee on Research on Law
Enforcement and Criminal Justice. Assembly of Behavioral and Social Sciences. Wash-
ington, DC: National Academy Press.
Rubin, P.H. (2009). Don’t scrap the death penalty. Criminology & Public Policy, 8(4), 853-859.
Shepherd, J.M. (2004). Testimony on Crime and Deterrence: Hearing on H.R. 2934, the
Terrorist Penalties Enhancement Act of 2003. Subcommittee on Crime, Terrorism, and
Homeland Security, House Judiciary Committee. Available: http://judiciary.house.gov/
legacy/shepherd042104.pdf [January 2012].
Shepherd, J.M. (2005). Deterrence versus brutalization: Capital punishment’s differing impacts
among states. Michigan Law Review, 104(2), 203-255.
Thomson, E. (1999). Effects of an execution on homicides in California. Homicide Studies,
3(2), 129-150.
Zimmerman, P.R. (2009). Statistical variability and the deterrent effect of the death penalty.
American Law and Economics Review, 11(2), 370-398.
