Wrongful Convictions in the United States: An Overview

In June 2013, Kirk Bloodsworth celebrated the twentieth anniversary of his exoneration from the brutal rape and murder of a 9-year-old girl. Identified by an anonymous tip and convicted largely on the basis of mistaken witnesses, Bloodsworth served nearly two decades in prison, some of that time on death row, for a crime he did not commit. With his release in 1993, Bloodsworth became the first individual released from death row because of postconviction DNA testing (Innocence Project, n.d., a). His name also graces a section of the Innocence Protection Act, which provides federal funding for the testing of biological evidence in cases of potential wrongful conviction.

The year 2013 also marks a century’s worth of study into the subject of erroneous convictions in America. In 1913, Yale law professor Edwin Borchard published his first study into “unjust convictions,” which became the starting point for a long tradition of research to follow. One hundred years later, the term wrongful conviction has become commonplace among scholars and practitioners who examine the workings—and failings—of criminal justice processes. But, what does it mean to declare a conviction “wrongful”? Brian Forst (2004) uses a broader term—errors of justice—which he argues includes both the conviction of the innocent and the failure to convict the guilty. Forst is undoubtedly correct that both phenomena reflect a failure of the criminal justice system, one presenting serious consequences that are difficult to quantify. Admittedly, there is limited research on the problem of false acquittals (Uviller, 1990), but to some extent the differential owes to the greater danger of wrongful convictions. In each case, a guilty defendant remains free, but wrongful convictions also bring the power of the state down upon an individual, subjecting him to the possibility of arrest, prosecution, conviction, and a sentence to years or, even worse, death, when he is innocent. It is not surprising, then, that Blackstone issued his famous admonition that “it is better that ten guilty persons escape than that one innocent suffer” (Blackstone, 1979, p. 358).

Even here, however, there is disagreement over what constitutes innocence—the term incorporating concepts of both factual and legal innocence. The former means the defendant did not commit the crime, whereas the latter penalizes the state for violating a defendant’s fundamental rights by overturning the ensuing conviction and in some cases ordering a new trial. Joshua Marquis, a district attorney from Oregon, has decried the improper usage of innocence in describing defendants who are released from prison on what some might consider a “legal technicality.” Says Marquis (2005, p. 521), “To call a man with blood on his hands innocent stains not only the truth, but calls into question the actual innocence of the fewer number who are truly exonerated.” To be sure, factual innocence and legal innocence may coincide in certain cases, where, for example, the constitutional violations that produce legal innocence also lead to the conviction of a factually innocent person. But, Marquis’s criticism suggests that we ought to be distinct in employing the term innocence.

Marquis’s (2006) critique extends to the prevalence of wrongful convictions. It is not so much that he denies wrongful convictions exist but that he claims the rate of wrongful convictions is miniscule—just .027% of criminal prosecutions. Marquis finds additional support from Justice Antonin Scalia, who has dismissed prior reports of wrongful convictions—calling them “fairly modest” in number (Kansas v. Marsh).

According to Simon (2006), the “overall rate of error in the criminal justice system is unknown and likely unknowable.” However, the figure is assuredly several times higher than that offered by Marquis and cited by Scalia. There are many empirical difficulties in estimating a rate of wrongful conviction, since in most cases researchers are extrapolating. For example, as Sam Gross (2008, p. 173) reminds us, the exoneration rate of 2.3% he uncovered with Barbara O’Brien (2008) came primarily from cases of rape and murder, “which together account for only 2 percent of felony convictions.” Certainly there are far more kinds of criminal prosecutions, but “lesser” felonies and certainly misdemeanors may lack the record, evidence, and interested advocates to investigate and pursue exonerations Moreover, the vast majority of criminal prosecutions are concluded by plea bargain, yet research offers few glimpses into errors there.

To address concerns such as these, Michael Risinger conducted a study in which he sought to match “apples to apples,” comparing known exonerations in capital rape-murders from the 1980s against a relevant denominator of cases. Although his study was based on a relatively small number of exonerations and a series of assumptions, he concluded that “a true minimum innocence rate for rape-murder[s] from 1982–1989” was at least 3.3% and potentially as high as 5% (2007, p. 778). In this respect, Risinger’s estimate was higher, but only slightly so, from Gross and O’Brien’s calculation of erroneous convictions in 2.3% of capital murder cases.

Although, the true rate of error in the criminal justice system is likely unknowable, research to date at least has narrowed the range of estimates to a span around 3%. Undoubtedly this puts the “success rate” of the criminal justice system well above 95%, but even an error rate of 3% would translate to upwards of 30,000 innocence individuals convicted each year. These are hardly the “modest” numbers posited by Marquis and Justice Scalia.

Edwin Borchard was not only among the first scholars to draw attention to erroneous convictions in the United States but his 1932 book, Convicting the Innocent, also established a methodological approach that would become the norm in subsequent research on the sources of wrongful conviction. Others followed him relatively closely (Frank and Frank, 1957; Gardner, 1952; Radin, 1964), but it took several decades before the research was taken up in earnest. In 1987, Hugo Bedau and Michael Radelet published an article in the Stanford Law Review detailing what they said were 350 cases in the United States of defendants erroneously convicted of capital or potentially capital crimes between 1900 and 1985. Their work caught the attention of lawyers and criminologists alike, culminating not only in an opposing article from officials in the Reagan Justice Department (Markman and Cassell, 1988) but also a seminal contribution from Radelet, Bedau, and a third coauthor, Constance Putnam (1992), further detailing their findings in a monograph. Since Borchard’s 1932 book, this was the first time that the public was truly confronted with multiple cases of alleged wrongful convictions.

Whereas Bedau and Radelet based many of their findings on personal assessments of case facts, the next wave of scholarship into wrongful convictions was to benefit from a seminal development in forensics—the arrival of DNA testing in the late 1990s. As anyone who watches crime dramas knows, DNA evidence represents a potential gold mine in criminal cases, permitting investigators to detect an individual’s presence at a crime scene. In certain crimes, primarily rape and murder, DNA evidence can identify the likely perpetrator where, for example, the suspect’s semen is found inside the victim or his skin cells are located under the victim’s fingernails.²

By the same token, DNA evidence can help clear innocent defendants who are erroneously linked to a crime or even convicted of one. This promise was first realized in 1989, when Gary Dotson, who had been convicted in Illinois 12 years earlier “based on a story fabricated by his presumed victim,” and whose ordeal to clear himself had been hampered by government misconduct, finally won his freedom when DNA testing showed that he could not have been the perpetrator of a crime the victim had by then disavowed (Northwestern Law School, n.d.).

DNA testing was further legitimized in 1996 when the National Institute of Justice (NIJ), the research and development agency of the US Department of Justice, released its report titled Convicted by Juries, Exonerated by Science: Case Studies in the Use of DNA Evidence to Establish Innocence After Trial (Connors et al., 1996). In a comprehensive study, independent researchers for NIJ examined 28 cases of wrongful conviction in which DNA testing had established innocence. Of the many important findings identified in the report, one particularly stood out: “Every year since 1989, in about 25 percent of the sexual assault cases referred to the FBI … the primary suspect has been excluded by DNA testing” (Neufeld and Scheck, 1996, p. xxviii). Put another way, among those rape cases referred to the FBI, law enforcement officers were wrong one quarter of the time in naming an initial suspect, their errors having been caught with the advent of DNA testing.

The NIJ report included commentary by Peter Neufeld and Barry Scheck, two former Legal Aid attorneys who, in 1992, founded the Innocence Project at Benjamin N. Cardozo School of Law. The Innocence Project (IP) is a nonprofit legal clinic that “handles cases where post-conviction DNA testing of evidence can yield conclusive proof of innocence. As a clinic, students handle the case work while supervised by a team of attorneys and clinic staff” (Innocence Project, n.d., b). The IP has now gained an international reputation as a leader in the investigation and reversal of wrongful convictions; today there is a national Innocence Network of activists working on wrongful convictions. Largely through the IP’s work, there have been over 300 postconviction DNA exonerations in the United States (Innocence Project, n.d., b).

To be sure, an innocent defendant may be exonerated through mechanisms other than DNA testing. For example, the National Registry of Exonerations, operated jointly by Northwestern and Michigan Law Schools, includes many defendants who established their innocence when lying witnesses recanted, new witnesses came forward, or other evidence was uncovered (National Registry of Exonerations, n.d.). Still, the process of exoneration is easier and the findings difficult to dispute when DNA testing is able to exclude a suspect to an almost certainty. It is no surprise, then, that the IP cites the number of defendants exonerated through DNA testing.

The exoneration of hundreds of innocent prisoners in the last two decades has had a powerful effect on academic scholarship, generating a virtual explosion of research on wrongful convictions (Leo, 2005); see also Findley (2011), Garrett (2011, 2008), Gross (2008, 1998, 1996), Huff (2013), Leo (2005, 2008), Medwed (2004, 2008), Redlich (2004), Simon (2012), Westervelt (2001), and Zalman (2011). The combination of this research “signaled a new and deepening interest in the study of miscarriages of justice by journalists and scholars unlike any time since Borchard’s founding work in the 1930s” (Leo, 2005, p. 204).

Strikingly, much of this scholarship has come from law professors and legal scholars, who have written extensively about the legal causes and consequences of wrongful conviction as well as about legal and policy reforms designed to reduce their occurrence (Leo and Gould, 2009). Collectively, the research has identified several factors most closely associated with erroneous convictions. Although certainly not dispositive, the most common factors include (1) mistaken eyewitness identification, (2) false confessions, (3) tunnel vision, (4) perjured informant testimony, (5) forensic error, (6) prosecutorial error, and (7) inadequate defense representation.

Nationally, over three quarters of known erroneous convictions (many of them in rape cases) are in part the result of mistaken eyewitness identifications (Garrett, 2011; Gross and Shaffer, 2012). Eyewitness misidentification is caused by natural psychological errors in human judgment (Loftus, 1996). As Gary Wells and colleagues have noted, stress alters people’s perception of an event. When confronted with a gun or other weapon during a violent crime, for example, the victim may focus so heavily on the firearm that he or she cannot take in and remember well the details of the perpetrator (Wells and Murray, 1983). This problem is more pronounced when the victim and perpetrator are of different races (Meissner and Brigham, 2001). Victims may believe that they recall the events accurately—the crime ostensibly “stenciled into their minds”—but research indicates that there is little relationship between an eyewitness’s certainty of her identification and the accuracy of that report (Wells and Murray, 1983).

Eyewitness identifications also can be influenced by the suggestiveness of the identification process, which “leads eyewitnesses to distort their reports of the witnessing experience across a broad array of questions” (Wells and Bradfield, 1998, p. 367). In practice, suggestion can enter the identification process in two ways. First, law enforcement officers or other observers can confirm a witness’s identification, whether at the time of the identification procedure or at any point before in-court identification (Rosenthal and Rubin, 1978). This can be as subtle as an officer praising the witness for a “good job” in her identification or as overt as a detective thanking the witness “for confirming our suspicion.” The problem with such suggestions is that they can give witnesses false confidence in their identifications, even if the witnesses are mistaken. Moreover, witnesses too rarely recognize that a reinforcing comment has inflated their confidence (Wells and Murray, 1983).

Second, law enforcement officers may employ suggestive identification procedures that make the suspect stand out from others. For example, in the case of Marvin Anderson, Anderson’s photograph appeared in color while the other photographs in the array were black and white (Gould, 2007). A further example is lineups, in which problems have arisen when the suspect is the only person presented of a particular height, hair color, or complexion among a group of six or more. These frailties may lead witnesses to make “relative judgments,” subtly encouraging them to select the individual in an identification procedure who looks most like the offender, rather than employing independent judgment to ensure that the individual identified is the actual perpetrator (Wells, 2008). Often, someone in a lineup or photo array looks more like the actual offender than the others do, and witnesses, in turn, may be tempted to identify that person (Wells et al., 1998). Additionally, any initial mistaken identification may reinforce subsequent reports, because eyewitnesses may confuse or replace their memory of the true perpetrator with the image of the person who looked most like the offender in the identification procedure (Gould, 2007).

Given documented problems such as these, US Attorney General Janet Reno commissioned a group of criminal justice professionals in the late 1990s to address and recommend guidelines for police identification procedures. Published by the National Institute of Justice in 1999, these guidelines provide the basis for best practices in law enforcement agencies around the country (Wells and Olson, 2003). The state of New Jersey, for example, has adopted the recommendations. Among these best practices, researchers recommend that witnesses be shown photographs or individuals in a lineup sequentially—that is, one at a time—rather than simultaneously as a group (National Institute of Justice, 1999). Researchers also recommend that each witness be asked to determine, upon looking at each photograph or individual, whether he or she recognizes the perpetrator. In an analysis of 25 studies comparing simultaneous and sequential identification procedures, scholars have estimated that sequential procedures can reduce the chances of a mistaken identification by nearly -half (Steblay et al., 2001). Perhaps most importantly, identification procedures must be administered “double blind,” so that neither the eyewitness nor the person administering the lineup knows the identity of the prime suspect and thus cannot guess about or hint at the correctness of the identification. In this way, suggestion and feedback effects can be minimized.

It is difficult for the public to understand why someone would confess to a crime that he or she did not commit (Leo and Liu, 2009), but research not only indicates that false confessions occur but also explains how they happen (Kassin et al., 2010; Leo, 2008). Several studies of erroneous prosecutions conducted since 1987 have shown that anywhere from 14% to 25% of the cases reviewed involved false confessions (Leo, 2008). When introduced into evidence at trial, false confessions usually lead to the conviction of the innocent (Drizin and Leo, 2004).

Police-induced false confessions are the product of a multiple-step process of influence, persuasion, and compliance. They usually involve psychological coercion (Ofshe and Leo, 1997). Under certain conditions of interrogation, police are more likely to elicit false confessions; moreover, certain types of individuals are more vulnerable to interrogation pressure and thus are more easily manipulated into giving false confessions.

Three errors occur in sequence when police elicit a false confession that leads to a wrongful conviction. The first error occurs when detectives mistakenly classify an innocent person as guilty. As Davis and Leo point out, “once specific suspects are targeted, police interviews and interrogations are thereafter guided by the presumption of guilt” (2006, p. 123). Although many cognitive errors lead police to mistakenly classify an innocent person as a guilty suspect, perhaps the most common errors are the product of their investigative training. Police officers in the United States are erroneously taught that they can learn to become human lie detectors, able to distinguish truth from deception at extraordinarily high rates of accuracy (Leo, 2008). However, social science studies have repeatedly shown that individuals are highly prone to error in their judgments about whether an individual is lying or telling the truth and thus are poor human lie detectors. Studies of police interrogators themselves find that officers cannot accurately distinguish between truthful and false denials of guilt at levels greater than chance (Hartwig et al., 2004).

The second and most common cause of police-induced false confessions is the use of psychologically coercive police interrogation methods (Leo, 2008). Unlike the old “third degree”—such as deprivation (of food, sleep, water, or access to bathroom facilities, for example), incommunicado interrogation, and extreme induced exhaustion and fatigue—today’s psychologically coercive techniques usually consist of implicit or explicit promises of leniency and implicit or explicit threats of harsher treatment in combination with other interrogation techniques such as accusation, repetition, attacks on denials, and false-evidence ploys (Leo, 2008; Ofshe and Leo, 1997).

Although psychological coercion is the primary cause of police-induced false confessions, individuals differ in their ability to withstand interrogation pressure and thus also in their vulnerability to giving false confessions (Gudjonsson, 2003). Individuals who are highly suggestible or compliant are more likely to confess falsely. So, too, are the developmentally disabled, cognitively impaired, juveniles, and the mentally ill—all of whom tend to be unusually suggestible and compliant (Kassin et al., 2010; Redlich, 2004).

Finally, false confessions are caused by undue suggestion or involvement by police officers in crafting or explaining a suspect’s admission. Most confessions consist of an “I did it” statement and a subsequent narrative—what researchers have referred to as the postadmission narrative (Leo and Ofshe, 1998)—that contextualizes and attempts to explain the “I did it” statement, transforming the admission into a confession. A detailed postadmission narrative is what makes the story appear to be a compelling account of the suspect’s guilt (Leo, 2008).

Police detectives use the postadmission phase of interrogation to influence, shape, and sometimes even script the suspect’s narrative. The detective’s ultimate objective is to elicit a persuasive account of what happened that will successfully incriminate the suspect and lead to his conviction. At the same time, if the detective pressures a suspect to accept a particular account or suggests crime facts to him, he can contaminate the suspect’s postadmission narrative and thus lay the groundwork for a false confession. When an interrogation is recorded, it may be possible to trace, step by step, how and when the interrogator implied or suggested the correct answers for the suspect to incorporate into his postadmission narrative. However, when the interrogation is not recorded—and the interrogations preceding virtually all of the documented false confession cases have not been recorded—then there may be no objective way to prove that the interrogator contaminated the suspect’s postadmission narrative even when the facts suggest otherwise.

Like any of us, police officers and prosecutors are susceptible to tunnel vision. That is, the more law enforcement practitioners become convinced of a conclusion—in this case, a suspect’s guilt—the less likely they are to consider alternative scenarios that conflict with this conclusion. As Findley and Scott (2006, p. 292) explain more comprehensively, when criminal justice professionals “focus on a suspect, select and filter the evidence that will ‘build a case’ for conviction, while ignoring the suppressing evidence that points away from guilt,” they are at risk of “locking on” to the wrong suspect and inadvertently leading to his continued prosecution and conviction.

Tunnel vision can occur at any point in the criminal justice process (Raeder, 2003). An officer may be so convinced of an eyewitness’s identification that he ignores other case facts that point away from the suspect’s guilt; a forensic scientist may conduct a hair comparison and see such a close match between that of the perpetrator and a suspect that she overlooks fingerprint analysis that isn’t as compelling; a prosecutor may be so satisfied with a suspect’s confession that she discounts forensic evidence that inculpates others; or a defense lawyer may consider the prosecution’s case so airtight that he doesn’t bother to look deeper into the government’s files. Any of these possibilities may explain why innocent individuals are named as suspects and prosecuted all the way to a conviction. These are not just theoretical possibilities; the many case studies of wrongful convictions show that errors attributable to tunnel vision are real and have grievous consequences (Gould, 2007).

A number of erroneous convictions have turned on the testimony of police informants who, themselves, lied for personal gain. As scholars note, informants are often rewarded without regard to the accuracy and reliability of their information (Zimmerman, 2001), with as many as one fifth of erroneous conviction cases based on snitches who lied (Natapoff, 2006). As a federal appellate judge has said of informant testimony, the government relies too heavily on witnesses who are “rewarded criminals,” which compromises both the accuracy and the legitimacy of the criminal justice system. “Because the government decides whether and when to use such witnesses, and what, if anything, to give them for their service, the government … can either contribute to or eliminate the problem” (Trott, 1996, p. 1382).

Given the rise and wide acceptance of DNA testing, it is possible to forget that, for decades, law enforcement had to rely on much less accurate forensic methods. Perhaps the most famous practice is fingerprinting, a method so common that applicants for many sensitive jobs have had to submit to a series of fingerprints. But evidence is now mounting about the problems of fingerprinting analysis (Cole, 2001), which include a lack of validity testing and an absence of validated standards for declaring a match (Mnookin, 2008). A 2009 report by the National Research Council strongly questioned the scientific reliability of fingerprint analysis (National Research Council, 2009, pp. 136–145).

Fingerprint analysis is hardly the most questionable forensic method employed. More troubling is hair comparison analysis, in which hairs found at a crime scene are compared under a microscope with those of a possible suspect. Although hair comparison analysis has passed the Frye (1923) and Daubert (1993) standards in many courts and has been admitted into evidence, more recent research raises considerable doubts about its accuracy (Gould and Leo, 2010). For example, the Law Enforcement Assistance Administration Laboratory Proficiency Testing Program, involving over 235 crime laboratories throughout the United States, found hair comparison analysis to be the weakest of all forensic laboratory techniques tested, with error rates as high as 67% on individual samples and the majority of laboratories reaching incorrect results on four out of five hair samples analyzed. Another study found that hair comparison error rates dropped from 30% to 4% when common hair comparison methods, which compare a questioned hair to the hair samples of a suspect, were changed to a “lineup” method, in which examiners compare a hair sample from the crime scene to samples from five potential suspects (Gould, 2007).

Another potentially problematic test has been serology analysis, which seeks to establish the probability that a perpetrator and suspect share the same blood type. By contrast to DNA testing, serology analysis does not specifically identify suspects, but jurors may not appreciate this fact, hearing testimony of similar blood types as proof of identity “with as much definitiveness as science can muster” (Moenssens, 1993, p. 13). Of course that is no longer the case.

DNA testing has helped to uncover the frailties of forensic methods used previously. This said, DNA is not a panacea. There is always the small probability that the results will be inaccurate, but, more importantly, few crime scenes have sufficient specific biological evidence for DNA analysis. A robber may never touch a victim or shed hairs or other biological markers in a spot specific to himself (Leo and Gould, 2010). Yet the most significant hurdle for many police departments is simply the cost of DNA testing (Pratt et al., 2006). Even large, well-funded departments with their own forensic labs, such as the New York Police Department, have cited cost as one reason why DNA testing is used in just 7% of homicide investigations (Schroeder and White, 2009). The prohibitive cost of DNA testing can make it a “tool of last resort” that departments turn to only after other pieces of evidence have been examined (Schroeder and White, 2009, p. 337). As a result, law enforcement often relies on other evidence, including different forms of forensic analysis that carry with them greater risks of inaccuracy.

Apart from the inherent weaknesses of various forms of forensic evidence, there have been several shocking examples of improper, indeed shoddy, laboratory practices and forensic testimony that have led to the conviction of innocent defendants (Garrett and Neufeld, 2009). Even the FBI, historically seen as the gold standard for forensic testing, has had to acknowledge serious potential mistakes by its crime lab and is now engaged in an audit of past cases (Hsu, 2012).

For the most part, American prosecutors conduct themselves ethically, seeking to mete out justice even if it means dismissing charges against a defendant whose criminality they suspect but cannot establish. Still, prosecutors may engage in overly suggestive witness coaching, offer inappropriate and incendiary closing arguments, or fail to disclose critical evidence to the defense, all of which may raise the prospect of an erroneous conviction (Medwed, 2008). In research on erroneous convictions, the most commonly established transgression is the prosecution’s failure to turn over exculpatory evidence. Sometimes police officers do not provide prosecutors with this evidence, or prosecutors may be unaware that they have such information in their files. In other cases, though, the misdeeds are intentional.

Consider the case of Edward Honaker, a man convicted for rape on the basis of testimony from the victim and her boyfriend. The prosecution never turned over an officer’s report that the victim had not been “allowed to clearly see the [perpetrator] during the entire sequence of events,” nor, more incredibly, did it reveal that the victim and her boyfriend were hypnotized 4 months after the crime, at which time they first identified Honaker’s photo as that of the rapist (Gould, 2007, p. 104). Instead, the prosecution’s witnesses were permitted to testify at trial, identifying Honaker, without the defense being aware that there were good grounds to doubt any identification. In cases like these, it is easy to see how the prosecution’s failure to disclose material exculpatory evidence can lead to an erroneous conviction.

Even if prosecutors fail in their duties, we expect a suspect’s attorney to zealously investigate and defend his case. As Bernhard (2001, pp. 227–228) explains, it is “the defense counsel’s responsibility to protect [the innocent] from the mistakes of others: from witnesses’ misidentifications, police officers’ rush to judgment, and prosecution’s reluctance to reveal potentially exculpatory material.” Yet, as a Columbia University study of capital appeals found, ineffective defense lawyering was the biggest contributing factor to the erroneous conviction or death sentence of criminal defendants in capital cases over a 23-year period (Liebman et al., 2000). The central reasons behind ineffective representation are inadequate funding, an absence of quality control, and a lack of motivation (American Bar Association, 2006). The attorney may be so rushed that she fails to communicate with his client or communicates “in a dismissive, callous or hurried manner” (Berry, 2003, p. 490). He She may make perfunctory attempts at discovery, if any; engage in a narrow or shallow investigation; neglect to retain needed experts or test physical evidence; fail to prepare for trial; or offer “weak trial advocacy and superficial or tentative cross-examination” (Berry, 2003, p. 490). The result is a cascade of errors that dilutes or even destroys the barrier provided by an effective advocate between an innocent defendant and an erroneous conviction.

As useful as the research to date has been in uncovering and exploring potential sources of erroneous convictions, its findings have largely been limited by the nature and scope of inquiry. Based initially on single case studies, researchers were unable to compare the factors that arose in a particular case of erroneous conviction with those that were found in other exonerations. More significantly, with few exceptions, researchers have not collected data on suitable control groups of cases. Even in those studies with control groups, the underlying crimes at issue have generally been serious felonies, often capital matters. As a result, while the field has been able to highlight particular sources of erroneous convictions, it has been unable to say with certainty whether these factors apply to a multitude of erroneous conviction cases or whether they are shared by other prosecutions that end in different results, including, for example, accurate convictions or acquittals. Put another way, we are still left wondering whether the sources identified to date are correlates or causes of erroneous convictions and if they are contributing or exclusive sources (Gould, 2007; Leo, 2005).

Up until recently, there had been four studies of wrongful convictions using case comparisons, two by criminologists (Harmon, 2001; Harmon and Lofquist, 2005) and two by nontraditional criminal law scholars (Garrett, 2011; Gross and O’Brien, 2008). Harmon used logistic regression equations to test which factors (i.e., independent variables) predicted judicial exonerations in capital cases, finding that the discovery of new evidence, allegations of perjury, and type of attorney were all statistically significant predictors of judicial exonerations in those cases. Harmon also determined that the amount of evidence introduced at trial was a statistically significant predictor of exonerations—namely that fewer types of evidence were used in capital cases that eventually resulted in exonerations.

In a second study, Harmon and criminologist William Lofquist (2005) compared not the innocent to the guilty in capital cases but the innocent to the innocent—81 judicial exonerations of innocent death-row prisoners with 16 executions of death-row prisoners they believed to be innocent. They found that allegations of perjury, multiple types of evidence, a suspect’s prior felony record, type of attorney at trial, and the race of the defendant were all significant predictors of case outcomes. In short, defendants who had a private or resource center lawyer representing them at trial (as opposed to a public defender) were significantly more likely to have their capital conviction (correctly) overturned and be exonerated than be (erroneously) executed. The same was true for convicted capital defendants whose prosecutors relied on fewer forms of evidence at trial, who raised allegations of perjury on appeal, who did not have a prior felony record, or whose case involved an African American defendant and a white victim. Of note, in Harmon and Lofquist’s study, the assumptions of innocence were made by the researchers, not by courts or other government officials.

Perhaps the most comprehensive study of wrongful convictions using a comparison sample method is Brandon Garrett’s (2008) analysis of the first 200 innocent prisoners who were released after postconviction DNA testing exonerated them. Of these, Garrett selected the 121 noncapital cases that contained a written decision and compared them to 121 noncapital cases that lacked DNA evidence showing innocence or guilt. The comparison sample was randomly selected using a Westlaw search to find all cases that had a published decision from the same state and same year as the DNA exoneration cases and involved a conviction for the same crime. Unlike the studies by Harmon and Lofquist, Garrett sought to understand how the criminal justice system handled the cases of persons erroneously convicted but eventually exonerated by postconviction DNA testing. The comparison sample, thus, provided a non-DNA control group of sorts, but, as Garrett points out, he did not know whether, or how many, in the comparison group were innocent. In addition, the comparison group contained less available information about the evidence supporting the convictions because there were no news reports about these cases, unlike in the DNA exonerations, many of which were high-profile.

Ironically, the real import of Garrett’s study for wrongful conviction scholars comes not so much from the comparison sample but from what his descriptive statistics of the first 200 DNA exonerations tell us: namely that courts repeatedly misjudged the defendants’ innocence and that lawyers, existing legal procedures, and actual innocence all failed to prevent these individuals from being convicted. Garrett also describes why this occurred. As he notes (2008, p. 131), ”These exonerees could not effectively litigate their factual innocence, likely due to a combination of unfavorable legal standards, unreceptive courts, faulty criminal investigation by law enforcement, inadequate representation at trial or afterwards, and a lack of resources for factual investigation that might have uncovered miscarriages.”

Samuel Gross and Barbara O’Brien (2008) have compared a sample of 105 cases of capital defendants who were sentenced to death and exonerated between 1976 and 2003 with a random sample of 137 executions carried out in the same period. Gross and O’Brien raise the question: What is unique about capital cases that lead to exonerations versus those that lead to execution? This is the same question Talia Harmon (2001) asked and analyzed earlier with a similar dataset.

Gross and O’Brien’s (2008) analysis implicitly assumes that the convicted capital defendants who were executed were guilty and the ones who were exonerated were innocent, although they are careful to qualify this point by attributing judgments about sufficiency of evidence to the legal system. Unlike Harmon and Lofquist’s (2005) study (which compared the innocent executed to the innocent exonerated) but like Harmon’s (2001) study, Gross and O’Brien (2008) compare the innocent exonerated to the guilty executed. Using chi-square tests rather than regression models, Gross and O’Brien identify several statistically significant differences between the capital convictions leading to exoneration and those leading to execution. Defendants who were exonerated were significantly less likely to be reported as mentally ill, more likely to have been tried for crimes that involved two or less victims, more likely to have been tried for crimes that involved children as victims, less likely to have confessed, more likely to have claimed innocence at trial, and more likely to have had an extensive criminal record (especially violent felonies). In addition, in the capital cases leading to exonerations, the time from crime to arrest was significantly much longer than in the cases leading to execution. Gross and O’Brien’s analysis demonstrates that these differences are modest predictors of exoneration in capital cases.

As useful as these studies have been, the field has largely lacked large-scale comparative research that extends beyond capital cases while employing advanced empirical methods. In early 2013, colleagues and I released results from a 3-year study of wrongful convictions that sought to extend research in this direction (Gould et al., 2013). Our study compared cases of wrongful conviction with a sample of “near misses,” cases where a factually innocent defendant was indicted but released before conviction on the basis of innocence. The comparison was posed to answer two overarching questions: (1) What factors explain why innocent suspects are erroneously convicted in certain cases but acquitted or have their charges dismissed in other cases? (2) What policy interventions will help the criminal justice system “get it right” and acquit the innocent, thereby preventing future erroneous convictions?

Our study included 460 cases from 1980 to 2012. Each case involved a factually innocent defendant who was indicted by a state for a violent felony against a person and was subsequently relieved of all legal responsibility for the crime. The project employed a conservative definition of factual innocence that clearly distinguishes it from innocence based on procedural error or other purely legal criteria (so-called legal innocence). Potential erroneous conviction and near-miss cases were systematically identified using the same, multifaceted methods, with researchers examining original records, scouring secondary sources, and conducting interviews with those involved to collect data that eventually populated more than 600 variables. We also used an instrument developed by the Police Foundation to assess the overall strength of the cases. The purpose was to allow us to distinguish between “easy” cases, in which few people would have considered a defendant to be guilty, and “harder” cases, where the facts of a case might have convinced many reasonable people to believe the defendant was guilty even though he was innocent.

In addition to bivariate and logistic regression analyses, we convened an expert panel of criminal justice professionals to review 39 sample cases in order to check and supplement the quantitative results. Noticeably, the panel independently identified as important most of the factors that we found to be statistical predictors of case outcome as well as additional aspects such as tunnel vision that we were not able to isolate via quantitative analysis. The panel discussion provided a valuable framework to understand how these factors interact within the criminal justice system to affect the progress of a case.

Together, our logistic regression model and the expert panel identified the following variables as significant factors that either harm or help the innocent defendant:

Interestingly, our analysis did not identify some of the traditional sources of erroneous convictions as significant predictors. These included the race of the defendant, snitch testimony, false confessions, police error, and many eyewitness testimony variables (such as interracial identification, certainty of the witness, and type of identification procedure). While these variables do not determine case outcome, some of them—like false confessions, police error, and an African American defendant—appear in a relatively large proportion of both the erroneous conviction and near-misses cases. We suggest that rather than being predictors of erroneous conviction, such factors may explain why innocent individuals are brought into the criminal justice system in the first place.

One of the conceptual contributions of our study is its distinction between those problems that lead to the indictment of the innocent and those that prevent the dismissal or acquittal of innocent defendants once they enter the criminal justice system. The question for criminal justice policymakers, then, is where in the process to focus attention. If the issue is what leads to the indictment of the innocent, then our findings point to mistaken identifications as well as false confessions and official misconduct. If, instead, one seeks to correct an erroneous indictment once it has occurred, then the focus should be on criminal defense practice, forensic evidence, and prosecutorial discretion, among other issues.

By no means was our research dispositive, and, in fact, there are many more issues that future research can help to address. Whereas we compared wrongful convictions to near-misses, other researchers would do well to contrast erroneous with accurate convictions or investigate different stages in the criminal justice process—for example, the decision to indict.

Be that as it may, as other scholars have noted (Gross, 2008), the preference for additional and even more detailed research should not cause us to lose sight from what we already know about the sources of wrongful conviction and the need for policymakers and practitioners to address those factors that are most open to remedy. Fortunately, wrongful convictions have begun to gain salience on the policy agenda, and, in more enlightened jurisdictions, lawmakers and criminal justice professionals have collectively advanced reforms that address some of the problems that produce erroneous convictions. There are now more than 75 innocence projects across the country (Innocence Project, n.d., b), so the issue of wrongful convictions is difficult to ignore. Nine states have created innocence commissions (Ostendorff, 2011), and more than 40 state legislatures have passed statutes to facilitate inmate access to biological evidence for postconviction DNA testing (Gould, 2007). Other states have implemented legislation to mitigate certain sources of erroneous conviction (Medwed, 2008). Even the US Congress has addressed erroneous convictions by passing the 2004 Innocence Protection Act, which provides funding for state postconviction DNA testing and raises the annual compensation for exonerated federal prisoners (Innocence Protection Act, 2004).

Apart from legislation, more and more law enforcement agencies and prosecutors’ offices are adopting procedures that can help reduce the possibility of erroneous arrest, indictment, and conviction. Based on a growing list of empirical evidence, a number of police departments have abandoned simultaneous identification procedures to follow double-blind sequential measures (Gould, 2007). With advanced technology now available in squad cars, some police agencies have even replaced the highly suggestive procedure of “show up” identifications with computer-generated sequential lineup procedures right at a crime scene. Audiovisual technology also has improved interrogations. When police questioning of suspects is videotaped, judges and juries have a more complete understanding of the circumstances surrounding confessions and thus can better weigh the reliability of any admissions. Those police departments that have employed videotaping generally have good reports of the process, saying it has cut down on frivolous claims of police brutality and convinced the truly guilty to plead guilty when their confession is obtained on tape (Gould, 2007). To implement these new methods and technologies, police and prosecutors in many jurisdictions now receive enhanced training, including scenario-based instruction on the problem of tunnel vision. It is one thing to appreciate the concept of tunnel vision in theory and quite another to follow an investigation start to finish to understand how a weak case can move forward even when it should be dropped or dismissed.

Perhaps most important in these measures and adaptations is the realization—by both criminal justice professionals and the public at large—that wrongful convictions do, in fact, occur. Twenty-five years ago, this conclusion was not well recognized in the United States. But with the rise of DNA testing and the exoneration of hundreds of innocent men and women, there is a growing awareness that the criminal justice system errs and that reforms are needed. Former Supreme Court Justice David Souter reflected this sentiment when he wrote that erroneous convictions (in capital cases) happen “in numbers never imagined before the development of DNA tests” (Kansas v. Marsh, 2006, p. 2544). After analyzing hundreds of post-1989 exonerations, Gross et al. (2005, p. 551) made this point even more forcefully: “any plausible guess at the total number of miscarriages of justice in America in the last fifteen years must be in the thousands, perhaps tens of thousands.”

Even if many of those cases have not been proven conclusively, the steady flow of news stories chronicling errors in the criminal justice process have had a significant influence on public opinion—reaching the point at which much of the public today believes that some defendants are, indeed, wrongly convicted (Smith, 2005). That realization alone is a significant step forward and provides hope that many of the sources of wrongful conviction eventually will be addressed. Reforms are ongoing, but there is still much more to accomplish.