Probability Of Conviction Research Articles

Authors’ Reply

Mr O'Doherty glosses over our most obvious finding: more and more doctors are being prosecuted for gross negligence manslaughter. The Crown Prosecution Service (CPS) cannot confirm or refute this, because they do not keep relevant statistics. We hope this will change. Mr O'Doherty criticizes us for using the published evidence to classify the aetiology of acts that have led to manslaughter charges. We recognized the difficulties with this approach in our article. We maintain that a doctor who makes a slip of the sort that is inevitable in human actions should not be judged criminally negligent, whatever dire consequences there are for the patient. This is consistent with the legal test that the CPS must of course apply, that the error was so bad that no reasonable doctor of the same level of experience, in the same situation, would have made that error. The Code of the CPS requires that, for a case to be brought, the jury should be more likely than not to convict.1 The outcome of any individual case is binary: ‘convicted’ or ‘acquitted.’ Laws of statistics apply even to lawyers. If the probability of conviction were exactly 0.5, then there would be just a 5% chance of the observed 14 convictions in 39 cases brought since the CPS and their colleagues in Northern Ireland were set up.2 The CPS can take no comfort from the fact that nearly a quarter of recent cases were abandoned before trial or dismissed by the judge. We impute no emotional motives to the CPS in our article. We do contrast society's desire for retributive justice with the desire to reduce deaths from errors. This is crucial. Society has to choose whether to exact retribution, or to minimize harm. All those involved need to realize that the two goals are inconsistent.

International Justice for International Crimes: An Idea whose Time Has Come

International criminal justice really began at Nuremberg in 1945, after an inauspicious start at Versailles in 1919. But little happened during the Cold War, and only in the 1990s, driven by a human rights movement that had refocused its energy on the rights of victims and concerns about impunity and accountability, did the efforts revive. The United Nations pioneered the activity, with three ad hoc tribunals. In 2002, a permanent institution, the International Criminal Court, began its operations. Concerns about the fairness of such proceedings have featured since the earliest days. In balance, both Nuremberg and its modern-day successors deliver acceptable judgments from a due process standpoint, although problems remain. Also troubling is an emphasis on convictions based upon paradigms that approach vicarious liability. This enhances the probability of conviction, but weakens the stigma of guilt and ultimately compromises the historical legacy. There is also a recent tendency to focus upon non-state actors, prosecuting rebels and terrorists rather than crimes of state.

The Optimal Magnitude and Probability of Fines with Court Congestion

This paper extends the law enforcement model to include court congestion. Society suffers harm from court congestion since delay affects the credibility and the reliability of the criminal justice system. The core result of the paper is that the probability of apprehension and the probability of conviction should be considered separately by the enforcement authority. Because the level of congestion is affected by the probability of apprehension only, the use of fines and conviction should be exhausted before resorting to the costlier (in terms of court congestion costs) instrument of apprehension.

Plea Bargains Only for the Guilty

A major concern with plea bargains is that innocent defendants might plead guilty. The law can address this concern. By restricting the permissible sentence reduction in a plea bargain, the law can preclude plea bargains in cases with a low probability of conviction (L cases). This will force the prosecutor to (1) select fewer L cases and proceed to trial with these cases or (2) select more cases with a higher probability of conviction (H cases) that can be concluded via a less costly plea bargain. As long as the probability of conviction is positively correlated with the probability of guilt, this selection‐of‐cases effect implies a reduced number of innocent defendants. We argue that the Federal Sentencing Guidelines achieve this socially desirable selection effect and that the recent Supreme Court holding in United States v. Booker dilutes this effect by reducing the guidelines' legal status from binding to advisory.

Can Making It Harder to Convict Criminals Ever Reduce Crime?

This paper attempts to find the optimal level of the burden of proof needed in criminal cases in order to minimize crime. It also aims to provide an explanation for the higher burden of proof required in criminal cases than civil cases. It assumes that police officers receive incentive payments for convictions in cases they investigate. Although the direct effect of a higher burden of proof requirement is to reduce the probability of conviction, the indirect effect is to force police officers to build stronger cases and put more effort into finding suspects who are more likely to be guilty. Moreover, the increase in the marginal probability of conviction potential criminals face when they actually commit a crime increases. These factors imply that a reduction in the burden of proof will not necessarily reduce crime.

Plea Bargains Only for the Guilty

A major concern with plea bargains is that innocent defendants will be induced to plead guilty. This paper argues that the law can address this concern by providing prosecutors with incentives to select cases in which the probability of guilt is high. By restricting the permissible sentence reduction in a plea bargain the law can preclude plea bargains in cases where the probability of conviction is low (L cases). The prosecutor will therefore be forced to - (1) select fewer L cases and proceed to trial with these cases; or (2) select more cases with a higher probability of conviction (H cases) that can be concluded via a less-costly plea bargain. As long as the probability of conviction is positively correlated with the probability of guilt, this selection-of-cases effect implies a reduced number of innocent defendants that accept plea bargains. We argue that the Federal Sentencing Guidelines in fact achieve, albeit inadvertently, this socially desirable selection effect. We further argue that more limited discretion in sentencing facilitates the selection-of-cases effect. In this respect, the Federal Guidelines are superior to the state-level guidelines that leave considerable room for discretion in sentencing.

State Executions, Deterrence, and the Incidence of Murder

This study employs a panel of state data over the years 1978-1997 to estimate the deterrent effect of the probability of apprehension, the probability of conviction given apprehension, and the probability of execution given conviction on the rate of per-capita murders. Particular attention is paid to problems of endogeneity bias arising from the non-random assignment of death penalty laws across states and a simultaneous relationship between murders and the deterrence probabilities. The primary innovation of the analysis lies in the estimation of a simultaneous equations system whose identification is based upon the employment of instrumental variables motivated by the theory of public choice as it relates to the criminal justice system and bureaucratic behavior. This is the first time such instruments have been used in the literature, and it is shown that these instruments are both statistically relevant and valid. The estimation results suggest that structural estimates of the deterrent effect of capital punishment are likely to be downward biased due to the influence of simultaneity. Correcting for simultaneity, the estimates imply that a state execution deters approximately fourteen murders per year on average.

"I Knew It All Along" Eventually: The Development of Hindsight Bias in Reaction to the Clinton Impeachment Verdict

Students estimated the chance that President Clinton would be convicted or acquitted in the U.S. Senate impeachment trial, at 4 points in time: (a) 22 days before the verdict (distal pretest), (b) 3 days before the verdict (proximal pretest), (c) 4 days after the verdict (immediate posttest), and (d) 11 days after the verdict (delayed posttest). Within-subjects analyses revealed that both foresight and hindsight changed over time. With respect to foresight, the perceived likelihood of conviction significantly decreased and the perceived likelihood of acquittal significantly increased between the 2 pretests. Content analyses of archived national news reports supported the notion that media predictions about the impending vote produced this temporal shift toward greater prospective accuracy. Confirming hypotheses, hindsight bias emerged for estimates of the prior probability of conviction, but not for estimates of the prior probability of acquittal. Within-subjects analyses revealed that 4 days after the ve...

"I Knew It All Along" Eventually: The Development of Hindsight Bias in Reaction to the Clinton Impeachment Verdict

Students estimated the chance that President Clinton would be convicted or acquitted in the U.S. Senate impeachment trial, at 4 points in time: (a) 22 days before the verdict (distal pretest), (b) 3 days before the verdict (proximal pretest), (c) 4 days after the verdict (immediate posttest), and (d) 11 days after the verdict (delayed posttest). Within-subjects analyses revealed that both foresight and hindsight changed over time. With respect to foresight, the perceived likelihood of conviction significantly decreased and the perceived likelihood of acquittal significantly increased between the 2 pretests. Content analyses of archived national news reports supported the notion that media predictions about the impending vote produced this temporal shift toward greater prospective accuracy. Confirming hypotheses, hindsight bias emerged for estimates of the prior probability of conviction, but not for estimates of the prior probability of acquittal. Within-subjects analyses revealed that 4 days after the verdict, participants accurately recalled that their prospective estimates of the likelihood of conviction had shifted toward greater accuracy over time; but 1 week later, they incorrectly believed that they had been more certain all along that Clinton would not be convicted. This article suggests that the potential losses associated with conviction were more salient than the potential gains associated with acquittal, and speculates that cognitive assimilation of the past did not occur until people had forgotten their earlier beliefs. These findings are important because they demonstrate that whether or not hindsight bias emerges depends not only on how long after the event people make retrospective judgments, but also how long before the event people focus these retrospective judgments. Supporting a self-serving interpretation, hindsight bias held for one's own estimates, but not for one's beliefs about the estimates of the average American or one's best friend. Consistent with Hawkins and Hastie's (1990) conclusions, a hybrid of cognitive and motivational accounts thus best explains the results.

Harmless Error

This paper presents an economic model of the harmful error rule in criminal appeals. We test the implications of the model against legal doctrines governing reversible and nonreversible error of criminal convictions and on a sample of more than 1,000 criminal defendants who appealed their convictions in the U.S. courts of appeals between 1996 and 1998. Among the more important theoretical and empirical findings of the paper are the following. Intentional prosecutor and judge errors are more likely to be found harmful and lead the appellate court to reverse the defendant's conviction than are inadvertent errors. Prosecutor errors are more likely to be forgiven than judge errors, in part because judge errors are likely to have greater influence on jurors. Errors are less likely to be harmful when defendants face a higher error‐free probability of conviction. Finally, appellate courts are more likely to publish an opinion when they are reversing the lower court.

Why Not Hang Them All: The Virtues of Inefficient Punishment

Replacing a criminal punishment with another that both is more severe and has a lower ratio of punishment cost to amount of punishment, while reducing the probability of conviction to maintain the same level of deterrence, lowers both punishment cost and enforcement cost. Hence imprisonment is always dominated by execution and both are dominated by fines and other alternatives. Moden legal systems do not fit that pattern. One possible explanation is that the ability enforces to profit by convictions and produce costly rent seeking. Examples include product liability litigation, civil forfeiture, and fraudulent prosecution motivated by rewards in eighteenth0‐century England. the problem was avoided by the use of infficient punishments in the legal system of saga period Iceland and the private norms of Shasta County, California. Execution, while not directly profitable for enforcers, facilitates rent seeking through threats leading to out‐of‐court settlements.

Relationship Between Pretrial Publicity and Trial Outcomes

Research suggests that pretrial publicity influences trials. Past research has relied heavily on experimental methods. Several commentators have questioned the ecological validity of the studies, and hence the value of the findings. The present study, one of the first to examine actual trials, focused on all federal murder trials over a 3-year period. The results suggested that (a) greater probability of conviction was associated with low rather than high levels of publicity; (b) defendants fared better under moderate rather than no publicity levels; and for defendants who were convicted, any degree of pretrial publicity was associated with longer sentences. In general, the results obtained from studying actual trials differed in important ways from the results obtained in laboratory research.

Bias in Jurors vs Bias in Juries: New Evidence from the SDS Perspective

Prior research by Kaplan and Miller (1978) suggested that juries are generally influenced less by extralegal, biasing information than individual jurors are. A social decision scheme (SDS) analysis of this question by Kerr, MacCoun, and Kramer (1997) suggested (a) that Kaplan and Miller's conclusion should hold only for relatively extreme legal cases (i.e., cases where the probability of conviction, without biasing information, was either very high or very low) and (b) that the opposite pattern should hold for moderate cases (with moderate conviction rates)—i.e., juries should show even greater sensitivity to biasing information than should individual jurors. An experiment is reported that compared juror vs jury sensitivity to biasing information (viz., prejudicial pretrial publicity) for versions of a legal case with a moderate and an extreme conviction rate. Consistent with the SDS analysis, juries were more biased than jurors for the moderate-case version, but the reverse was true for the extreme-case version. The implications of these findings and the more general utility of the SDS model for studying group processes are discussed.

Effects of Defendant Ethnicity on Juries' Dispositions of Felony Cases1

This research examined jury decisions in 317 noncapital felony cases in El Paso, Texas, and assessed the impact of juror ethnicity on jury trial outcomes. Results revealed that there was no relation between defendant ethnicity and the probability of conviction. Anglo American defendants, however, received sentences that were approximately twice as severe as Hispanic defendants. Sentences imposed by juries were significantly related to defendant ethnicity and type of crime for which they were tried. Sentences were also influenced by defendant ethnicity in interaction with jury ethnic composition. Important differences appeared when there was a critical mass of 6 or more Hispanics on juries. This study, using criminal court data, provides a unique opportunity to examine the utility of social psychological theories for understanding actual trial outcomes.

Criminal Law and Behavioral Law and Economics: Observations on the Neglected Role of Uncertainty in Deterring Crime

Two similarly situated individuals commit identical crimes. The first is sentenced to 10 years in prison while the second is sentenced to 5 years. The disparity between the two sentences of the criminals is a reason for concern. The person who is sentenced to 10 years has a legitimate moral complaint: was I sentenced more harshly than she was. In contrast, two individuals commit identical crimes. When the first criminal commits the crime, the police invest few resources in detecting criminals of this particular sort. Consequently, the probability that the criminal will be detected is merely ten percent. When the second criminal commits the crime, the police conduct a major campaign against crimes of this sort and consequently the probability facing the second criminal is twenty percent. The latter case although creating disparate treatment of similarly situated criminals does not raise the same type of moral resentment raised by the first case. The moral concern of the person who asks why me? is compelling when there is a disparity in the sentences, but has no moral force when the relevant disparity is disparity with respect to the probability of detection. Various established doctrines and practices reflect the difference in our moral intuitions between disparity with respect to the size of the sanction and disparity with respect to the probability of detection. Sentences are public; they constitute part of our criminal law. But no criminal code provides any information with respect to the rate of detection, or conviction. Moreover, a criminal sanction cannot be imposed retroactively in our system. On the other hand, a person who committed a crime while the probability of detection was low cannot complain that she was caught simply because the probability of detection increased after she had committed the crime. Last, the probability of detection often changes due to temporary enforcement campaigns initiated by the police. No analogous sentencing campaigns during which judges impose heavier sanctions relative to the ones imposed on criminals who are tried at other times exist in our legal system. In sum, criminal sanctions are public, relatively stable and consequently relatively predictable. In contrast, the practices governing the determination of the probability of conviction reinforce uncertainty. The paper explores ways of reconciling the different treatments of certainty in the legal system. The overriding normative principle that governs the determination of certainty can be stated as follows. The criminal law system aims at providing maximum deterrence at minimal costs. The costs of the criminal law system are determined by the costs of sentencing and by the costs of the detection and conviction systems. Since the cost of sentencing depends on the average sanction, the first question to answer is what is worse from the potential criminal's point of view: a sentencing scheme which guarantees certainty with respect to the size of the sanction, or a sentencing scheme which does not guarantee such a certainty. Similarly since the costs of detection and conviction depend on the average probability of detection and conviction, the first question is what is worse from the potential criminal's point of view: a detection and conviction scheme which guarantees certainty with respect to the probability of detection and conviction, or a scheme which does not guarantee such a certainty. Once we discover which scheme is worse from the perspective of the criminal, the State should adopt this scheme since it has larger deterrent effects. Thus, if one finds out that potential criminals prefer a sentencing scheme that does not guarantee certainty, the State should adopt a sentencing scheme that is certain. Similarly, if one finds out that criminals prefer a sentencing scheme, which guarantees certainty with respect to the probability of detection and conviction, the State should adopt a sentencing scheme that guarantees uncertainty. Our paper invokes insights from psychological experiments to examine the attitudes of criminals towards uncertainty and illustrates that criminals are likely to prefer a scheme in which the size of the sentence is uncertain while the probability of detection and conviction is certain. Consequently, we argue that the choice to increase certainty 1with respect to the size of the sentence and to decrease certainty with respect to the probability of detection and conviction can ultimately be justified on efficiency-based grounds.

Hindsight Bias in Reaction to the Verdict in the O.J. Simpson Criminal Trial

Students estimated the chance that O.J. Simpson would be convicted or acquitted of murder and the likelihood of large-scale violence following conviction, at 3 points in time: 2 hr before the announcement of the not guilty verdict, 2 days after the verdict, and 1 week after the verdict. Within-subjects analyses revealed that estimates of the probability of conviction made 2 hr before the not guilty verdict were higher than estimates of prior probability made 2 days after the verdict. Supporting hypotheses, the tendency to recall a higher chance of conviction after the verdict was strongest among those who initially perceived acquittal to be least likely. Contrary to predictions, however, the perceived probability of acquittal did not significantly increase until 1 week after the verdict. Estimates of the prior likelihood of violence following a guilty verdict also increased immediately after the verdict and remained high 1 week later. Results are discussed in terms of the influence of mass media and cognitive processes on the development of hindsight bias over time.

Hindsight Bias in Reaction to the Verdict in the O. J. Simpson Criminal Trial

Students estimated the chance that O.J. Simpson would be convicted or acquitted of murder and the likelihood of large-scale violence following conviction, at 3 points in time: 2 hr before the announcement of the not guilty verdict, 2 days after the verdict, and 1 week after the verdict. Within-subjects analyses revealed that estimates of the probability of conviction made 2 hr before the not guilty verdict were higher than estimates of prior probability made 2 days after the verdict. Supporting hypotheses, the tendency to recall a higher chance of conviction after the verdict was strongest among those who initially perceived acquittal to be least likely. Contrary to predictions, however, the perceived probability of acquittal did not significantly increase until 1 week after the verdict. Estimates of the prior likelihood of violence following a guilty verdict also increased immediately after the verdict and remained high 1 week later. Results are discussed in terms of the influence of mass media and cogni...

From Poisson to the present: Applying operations research to problems of crime and justice

In the 1830s Simeon-Denis Poisson developed the distribution that bears his name, basing it on the binomial distribution. He used it to show how the inherent variance in jury decisions affected the inferences that could be made about the probability of conviction in French courts. In recent years there have been a number of examples where researchers have either ignored or forgotten this inherent variance, and how operations research, in particular mathematical modeling, can be used to incorporate this variance in analyses. These are described in this paper, as well as other contributions made by operations research to the study of crime and criminal justice.

CRIMINAL DETERRENCE IN THE REDUCED FORM: A NEW PERSPECTIVE ON EHRLICH'S SEMINAL STUDY

Ehrlich [1973] is perhaps the best known and most influential study of criminal deterrence. Ehrlich's structural estimation of a three‐equation simultaneous system found large and significant direct deterrent effects of penalties on crime rates. However, recent theoretical results show that higher penalties may indirectly increase crime rates by reducing the probability of conviction. Hence, a reduced‐form model is needed to learn the total effect of penalties on crime rates. Using such a model, we find that the marginal deterrent effects reported by Ehrlich vanish. This result generates much different policy implications than those widely adopted following Ehrlich's publication.

The Adjudication Of Rape Since Reforms: Examining The Probability Of Conviction And Incarceration At The National And Three State Levels

This paper examines trends in the criminal justice system's handling of rape cases since the implementation of reforms both nationally and in three states: California, New York and Pennsylvania. While previous research has remained equivocal regarding the instrumental effects of rape law reforms, this study has documented the usefulness of more refined methodologies with which to address this issue. Included in these reformulations were more refined dependent measures of rape (age and gender specific); the inclusion in the analysis of equivalent trends for robbery to control for extraneous factors that may increase these adjudication outcomes for all violent crimes; and, finally, more liberally defined time periods which include data from the late eighties. This last reformulation is particularly important since original statutes in most states have undergone extensive interpretation based on recent appellate court decisions. When these methodological reformulations were made, results indicated that conviction rates for rape increased over and above increases observed for robbery in all three states. While rates of incarceration also increased in all states for rape, only in Pennsylvania and at the national level did these increases exceed those observed for robbery. While proponents of rape law reform would not necessarily characterize the picture painted by these findings as a perfect one, this research demonstrates the importance of utilizing more refined measures and methodologies with which to examine trends in the adjudication of rape since reforms.