Skip navigation
The Habeas Citebook: Prosecutorial Misconduct - Header
× You have 2 more free articles available this month. Subscribe today.

Expert Forensic Testimony Flawed by Implicit Racial Bias

by Casey J. Bastian

The unnecessary deaths of George Floyd and Breonna Taylor are examples of incidents that have raised public awareness and hastened conversations about racial bias in the criminal justice system. Reforms in policing have received the lion’s share of people’s attention. However, the possibility of racial bias extends throughout the system.

One such area is forensic sciences and the resulting expert forensic testimony. Expert scientific evidentiary conclusions are readily accepted without question by judges, jurors, and lawyers. Government experts especially receive a free pass and are unquestionably believed, presumed to be neutral and objective witnesses who only rely on scientific facts and accurate professional opinions. However, that isn’t always the case; it appears that such experts are just as susceptible to implicit racial bias as any other witness. These experts may actually be averring to information subconsciously contaminated by bias resulting in flawed conclusions.

An in-depth analysis of this phenomenon is found in “Perpetuating the Presumption of Guilt: The Role of Implicit Racial Bias in Forensic Testimony,” by Janice C. Puracel, J.D., and Aliza B. Kaplan, J.D. Puracel is Executive Director of the Forensic Justice Project, and Kaplan is Professor at, and Director of, the Criminal Justice Reform Clinic at Lewis and Clark Law School.

The study initially identifies those expert methods for “pattern matching” are particularly subject to bias contamination. These methods include the analysis of tool mark and firearm impressions, latent prints, hair, bloodstain, and footwear and tire impressions, et cetera. They are inherently subjective, relying on the examiner’s individual judgment, instead of more objective forensic standards.

A major problem is with examiners being given “irrelevant contextual information.” Instead of only being given the evidence to examine—such as a bullet from a crime scene—the expert is also given the name, race, or background of a suspect. Data suggest that such information can predispose the examiner to render a results-driven opinion. The human eye will see what the mind wants it to see. Reflecting a bias in favor of guilt, rather than an objective determination that the bullet, in our example, actually possesses the marks constituting forensic evidence matching that evidence to the correct firearm.

Data also suggest that the inclusion of “irrelevant contextual information” only adds to the inherent predisposition towards guilt. The study argues that such information only adds to the racial bias, and its impact is often hard to ascertain as it is “unspoken and rooted in decades of societal learning that has created presumptions about dangerousness, culpability, and propensity toward violence based on race.” Citing the number of recent exonerations as proof of implicit racial bias, it seems irrefutable that faulty forensic testimony results in wrongful convictions. There are many criminal appeals where the examiners’ original opinion changes from “certain and inculpatory” to neutral or even exculpatory. The evidence doesn’t change, and nothing new is added to it. The only thing that changes is that the expert opinion actually becomes objective.

Patrick Pursley is a Black man who was convicted in 1994 for murder. The conviction was based solely on the opinion of a firearms expert. The expert testified that the test fires from a firearm attributed to Pursley matched the bullets and cartridge cases found at the crime scene. The expert testified that the pistol was the murder weapon “to the exclusion of all others.” Pursley was sentenced to life without parole.

He would spend the next 22 years in prison before that same expert testified at a post-conviction hearing that the examination was now “inconclusive.” Two new experts would exclude the pistol as the murder weapon. At a new trial, the court agreed, and on January 16, 2019, Pursley was exonerated. Pursley was awarded a certificate of innocence two years later. A reasonable question arises: what would lead the original expert to provide such a definitive, but incorrect, conclusion if it was NOT the result of the role racial bias plays in the process?

The exoneration of another Black man, Zavion Johnson, highlights the role of jurors presuming dangerousness under the guise of “science” plays in wrongful convictions. In 2002, Johnson was convicted of assaulting and murdering his four-month-old daughter Nadia. Medical experts testified for the prosecution that Nadia had been “violently shaken resulting in her death.” Even the judge believed that the evidence “was overwhelming that [Nadia’s death] was not an accident.” Johnson consistently stated that Nadia had slipped from his hands while being given a bath and hit her head on the bathtub’s edge. Thirteen witnesses testified that Johnson “was a loving, caring, calm, and patient father.” The jury believed the violent abuse narrative perpetuated by the so-called experts.

Fifteen years later, two of the original experts recanted their trial testimony and testified that Nadia’s injuries were not “solely diagnostic of abuse,” and accidental injury could not be excluded. Two new experts testified that the injuries sustained by Nadia were consistent with the events as described by Johnson. The government would eventually dismiss all charges.

The National Registry of Exonerations (“NRE”) contains dozens of cases similar to Pursley’s and Johnson’s. The plight of the exonerated highlights the subjectivity of forensic testimony, the role of implicit racial bias resulting from that testimony, and the power to reinforce inherent racial biases of fact finders. A number of cases highlight wrongful convictions wherein faulty forensic expert testimony is the sole basis of the conviction. So many of these cases involve a person of color, highlighting the urgent need to excise implicit racial bias from forensics.

Implicit racial bias is also known as “unconscious bias” and has been extensively documented. Implicit bias can either be “attitudes or stereotypes that affect our understanding, decision-making, and behavior without our even realizing it.” Courts have noted the “growing body of social science [that] recognizes the pervasiveness of unconscious racial and ethnic stereotyping and group bias.” Social scientists have utilized various measures and research paradigms to reach these conclusions over the last several decades. Study data confirm that “implicit bias is pervasive (widely held), large in magnitude (as compared to standard measures of explicit bias), dissociated from explicit biases (which suggests explicit biases and inherent biases, while related, are separate mental constructs), and predicts certain kinds of real-world behavior.” The impact of implicit bias on the criminal justice system is really not debatable today.

Even 25 years ago, Justice O’Connor in Georgia v McCollum, 505 U.S. 42 (O’Connor, J., dissenting), wrote, “[i]t is by now clear that conscious and unconscious racism can affect the way white jurors perceive minority defendants and the facts presented at fair trials, perhaps determining the verdict of guilt and innocence.”

The presumption of guilt that people of color must overcome, which is seemingly imbedded in the criminal justice system, seems to exist due to “decades of dehumanization through false narratives that portray them as dangerous, uneducated, and menacing.” The presumption is difficult to expose or rebut because it is not always perceptible, let alone intentional. Implicit biases against people of color are long-standing and deep-seated, built into our culture and criminal justice system.

In the early 1980s, the U.S. government capitalized on the myths and stereotypes held by citizens of this country. Advancing disparate policies based on racial profiling, such as mandatory minimums, stop-and-frisk, crack-versus-powder cocaine sentencing, and news stories about the mythological “superpredator” and “crack babies.” These policies and myths were modern radicalized beliefs amplifying fears in society at that time.

The Reagan Administration expanded policies into what became known as the “war on drugs” and enacted the Anti-Drug Abuse Act (“ADAA”). These Reagan-era policies set the stage for racializing drug policy by focusing on two drugs frequently possessed by Black and brown Americans: crack cocaine and marijuana. The ADAA increased law enforcement size and funding, leading to the over-policing of these communities. The ADAA also “legally equated drug use and distribution with violent crime.”

This was nothing new. In the 1870s, it was the dangers of opium and Chinese immigrants. The 1920s saw an attempt to link marijuana use and Hispanic dangerousness. The ADAA also oriented the focus of drug sentencing from a rehabilitation-based system to a punishment-based one. The U.S. prison population doubled during the Reagan Administration, with Blacks comprising almost half of that population. That administration used the media to embed racial stereotypes into our belief systems by flooding American living rooms with narratives of rampant drug abuse and violence in communities of color. This was used to justify harsh penalties and influence juror perceptions, leading to the eventual dramatic rise in conviction and incarceration rates in American society.

The Civil Rights Movement made explicit racism unpalatable. Yet the same culture allowed polices to develop that seemed to focus on the supposed poor morals and character of people of color. This presumed connection between criminality and race is prevalent today as a result of the “deep roots with which it has been embedded into our subconsciousness.” As a result, the NRE data show that of 2,810 exonerations, 64 percent involved people of color. A 2017 NRE report found that innocent Black people were “12 times more likely to be convicted of drug crimes and seven times more likely to be convicted of murder than White people.”

These data-driven realizations have helped increase the scrutiny on the intersection of racial bias and the criminal justice system. Its impact on policy, arrests, prosecutorial-charging decisions and plea offers, juror perception, and sentencing have all received scholarly attention. The fallibility of the human component has been recognized in all of these areas. But for unknown reasons, forensic sciences are still widely viewed as “exacting, infallible, and even mechanical” despite its overwhelming human component. Even the 2009 National Academy of Sciences (“NAS”) report on problems in forensic sciences did not at all mention racial bias as a likely contributing factor.

Despite these challenges, broad insights are rapidly evolving concerning the fallibility of forensic methods. The need to recognize that forensic sciences may not be as inherently reliable as currently believed is imperative; nearly half of the DNA exonerations, and one-quarter of total exonerations, involved faulty or misleading forensic evidence. This seems to be a result of forensic methods lacking scientific validation and objective standards as “data from validation studies [] has been manipulated to drive error rates down and give the false impression that the methods are near perfect.”

The study identifies two keys concerns about the role implicit racial bias plays in forensic testimony. First, faulty forensic testimony that is relied upon opens the door to convictions based on racial bias. Humans tend to “naturally focus on similarities between samples and discount differences” when pattern-matching. Second, the discretion of the analyst throughout the process may encourage bias and affect the outcomes of the forensic testing. Most forensic methods are subjective, depending on human judgment. More human judgment equals more subjectivity in the methodology.

Experts may also be “influenced by extraneous information and external pressures about a case.” Being informed of the race of a suspect can skew analyst conclusions towards guilt, even when it is entirely unintentional. Citing other studies, the study explains: “When forensic evidence is placed in the hands of an individual, it becomes viewed under that person’s own lens and is susceptible to judgment based on how one’s brain processes experiences and information it receives. In a practice that is already open to subjectivity, there will inevitably be decisions made that reflect inherent prejudices about people of color.”

One of the most significant impediments to realizing change is “bias blind spot.” We tend to believe the problem is “other” people—“others are biased but we ourselves are not.” Researchers suggest that effortful relearning and proactive solutions to limit irrelevant contextual information should be areas of focus in the forensic expert’s arena.

The study also suggests auditing forensic lab policies to minimize irrelevant contextual information and reduce discretion. For example, there is no universal objective standard as to how many similar marks create a “match,” allowing for the entirely subjective opinion that a suspect firearm is the actual source of the ballistic evidence. The NAS has also recommended that public forensic labs be removed from the control of law enforcement to ensure independence while reducing confirmation and contextual bias.

Legislators could also mandate specific protocols be developed for root cause analysis in state-run labs. This could be a resolution to many problems as the experience and knowledge of other disciplines, such as engineering and aviation, use root cause analysis to prevent unwanted outcomes from recurring. “Root cause analysis is a process that identifies, in an objective blame-free environment, why an adverse event or near miss occurred.” This process allows systems to be improved by focusing on “how or why something happened, rather than seeking to assign blame.” This would allow for the development of corrective actions in the field of forensic sciences, resulting in greater effectiveness as well as increased cost-efficiency.

The responsibility is also on defense attorneys to thoroughly cross-examine forensic experts on implicit bias even if it is assumed the expert “is still a good or decent person.” The study lays out dozens of specific inquiries a diligent defense attorney could make upon a forensic expert to minimize or expose the impacts of inherent racial bias.

There is no longer a question of whether there is the evidence of racial bias. The evidence abounds in the field of forensic science as a result of decades of research, data on disparate outcomes, written and unwritten lab policies that introduce irrelevant contextual information on a routine basis, and obvious levels of unnecessary individual discretion in too many forensic methods. We must insist that expert opinions are not needlessly influenced by hidden biases to protect forensic evidence just as we would with any other evidence. It is crucial to our pursuit of justice that we eliminate any role implicit racial bias may play in creating false forensic testimony, which far too frequently has caused wrongful convictions.  

Source: Kaplan, Aliza B. and Puracal, Janis, Perpetuating the Presumption of Guilt: The Role of Implicit Racial Bias in Forensic Testimony (August 19, 2021). Criminal Law Bulletin, forthcoming volume 58 (2022).

As a digital subscriber to Criminal Legal News, you can access full text and downloads for this and other premium content.

Subscribe today

Already a subscriber? Login



CLN Subscribe Now Ad 450x600
Advertise Here 4th Ad
Disciplinary Self-Help Litigation Manual - Side