Rate of false conviction of criminal defendants who are sentenced to death

Edited by Lee D. Ross, Stanford University, Stanford, CA, and approved March 25, 2014 (received for review April 5, 2013)
April 28, 2014
111 (20) 7230-7235

Significance

The rate of erroneous conviction of innocent criminal defendants is often described as not merely unknown but unknowable. We use survival analysis to model this effect, and estimate that if all death-sentenced defendants remained under sentence of death indefinitely at least 4.1% would be exonerated. We conclude that this is a conservative estimate of the proportion of false conviction among death sentences in the United States.

Abstract

The rate of erroneous conviction of innocent criminal defendants is often described as not merely unknown but unknowable. There is no systematic method to determine the accuracy of a criminal conviction; if there were, these errors would not occur in the first place. As a result, very few false convictions are ever discovered, and those that are discovered are not representative of the group as a whole. In the United States, however, a high proportion of false convictions that do come to light and produce exonerations are concentrated among the tiny minority of cases in which defendants are sentenced to death. This makes it possible to use data on death row exonerations to estimate the overall rate of false conviction among death sentences. The high rate of exoneration among death-sentenced defendants appears to be driven by the threat of execution, but most death-sentenced defendants are removed from death row and resentenced to life imprisonment, after which the likelihood of exoneration drops sharply. We use survival analysis to model this effect, and estimate that if all death-sentenced defendants remained under sentence of death indefinitely, at least 4.1% would be exonerated. We conclude that this is a conservative estimate of the proportion of false conviction among death sentences in the United States.

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Acknowledgments

We thank the following for their assistance and advice: Dr. Roderick J. A. Little (Richard D. Remington Collegiate Professor of Biostatistics and Professor, Department of Statistics, University of Michigan), Dr. Richard Gonzalez (Professor, Department of Psychology and Department of Statistics and Business School, University of Michigan), Dr. John DiNardo (Professor, Department of Economics and School of Public Policy, University of Michigan), and Dr. J. J. Prescott (Professor, Law School, University of Michigan).

Supporting Information

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Supporting Information

References

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Information & Authors

Information

Published in

The cover image for PNAS Vol.111; No.20
Proceedings of the National Academy of Sciences
Vol. 111 | No. 20
May 20, 2014
PubMed: 24778209

Classifications

Submission history

Published online: April 28, 2014
Published in issue: May 20, 2014

Keywords

  1. capital punishment
  2. criminal justice
  3. wrongful conviction

Acknowledgments

We thank the following for their assistance and advice: Dr. Roderick J. A. Little (Richard D. Remington Collegiate Professor of Biostatistics and Professor, Department of Statistics, University of Michigan), Dr. Richard Gonzalez (Professor, Department of Psychology and Department of Statistics and Business School, University of Michigan), Dr. John DiNardo (Professor, Department of Economics and School of Public Policy, University of Michigan), and Dr. J. J. Prescott (Professor, Law School, University of Michigan).

Notes

*This Direct Submission article had a prearranged editor.
A reviewer of an earlier draft suggested an alternative analytic approach. The suggested approach postulates a campaign process that gives some but not all death-sentenced defendants the opportunity to be exonerated. Identification of the false conviction rate is then based on independence assumptions between innocence and removal from death row. With more complete data of the sort required for the best realization of this insightful approach, we believe that it would offer a particularly valuable supplement, and test of the robustness, of our findings and conclusions.

Authors

Affiliations

Samuel R. Gross1 [email protected]
University of Michigan Law School, Ann Arbor, MI 49109;
Barbara O’Brien
Michigan State University College of Law, East Lansing, MI 48824;
Chen Hu
American College of Radiology Clinical Research Center, Philadelphia, PA 19103; and
Edward H. Kennedy
Department of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104

Notes

1
To whom correspondence may be addressed. E-mail: [email protected].
Author contributions: S.R.G. and B.O. designed research; S.R.G. and B.O. performed research; C.H. and E.H.K. analyzed data; and S.R.G. and B.O. wrote the paper.

Competing Interests

The authors declare no conflict of interest.

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    Rate of false conviction of criminal defendants who are sentenced to death
    Proceedings of the National Academy of Sciences
    • Vol. 111
    • No. 20
    • pp. 7163-7498

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