The Role of Forensic Evidence in the Legal System: Potential for Bias and Objectivity

Though we typically view science as an empirical, objective resource used to uphold our justice system through evidentiary results, attorneys often obtain experts' knowledge of evidence to prove their cases rather than seek veracity. In the landmark case, The People of the State of California v. Orenthal James (O.J.) Simpson (1994), 150 million Americans witnessed the impact of scientific evidence used subjectively, as litigation on both sides centered their arguments on racial polarization rather than the murder trial itself.[1]While an attorney’s personal biases can influence a case's outcome, the integrity of the law should always remain a practitioner's priority by utilizing science as the foundation for a legal claim rather than a secondary resource to prove a preconceived argument. “Science seeks empirical truths regardless of their implications, and scientists ideally share a common truth-seeking mission,” as stated by legal scholars Shari Seidman Diamond and Richard O. Lempert.[2] Thus, while personal bias is innate to human nature, the legal system necessitates an active commitment to impartiality, both from litigators and experts. Many attorneys utilize the expertise of scientific professionals for this exact reason: to gather and report on information to provide a precise and impartial interpretation of the forensic analysis of a case.[3] By exploring this complex topic, we can conceptualize how scientific evidence is used in the legal system. As a tool for biased litigation, it can violate the fundamental impartiality of the law. As a tool for just litigation, it is one of the most integral components for facilitating objective legal processes.

As scientists are, to an extent, removed from a case's stakes, they can ideally provide expert opinion from an external perspective. Still, there are substantial risks to the neutrality of the case, as litigators may use evidence to persuade the judge and jury rather than extrapolate truth.[4] A prime example of this phenomenon is best recognized in the The People of the State of California v. Orenthal James (O.J.) Simpson (1994) murder trial, where football running back O.J. Simpson was prosecuted for the alleged murder of his ex-wife, Nicole Simpson, and her 25-year-old friend, Ron Goldman.[5] Due to a lack of witnesses at the crime scene, the prosecution and defense heavily relied on scientific evidence to elucidate their arguments. In July of 1994, lead prosecution attorney Marcia Clark and lead defense attorney Robert Shapiro debated before Judge Lance Ito regarding how DNA evidence from the crime scene should be processed. The defense argued that the private company the prosecution employed, Cellmark Diagnostics, did not have credibility nor claim over the DNA; while Clark offered to let the defense witness the DNA processing, Shapiro argued that it was purposeless, and instead, 50 percent of the DNA should be given to the defense for their private processing.[6] Ultimately, Judge Ito sided with Clark. Though he did not find merit in the defense's claims, this discourse mainstreamed concerns about the potential of subjectivity between litigation and experts regarding evidentiary analysis.[7]

On a grander scale, litigators' bias influences the interpretation of evidence and the perceived objectivity of expert testimony. Notably, Los Angeles Police Department (LAPD) Detective Mark Furman, a first responder at the crime scene, later discovered the Simpson cases’ “infamous black glove”: a piece of evidence that immediately became the cornerstone of the trial, with viewership waiting to see if it fit Simpson’s hand and ultimately proved his guilt. The Simpson defense, however, contested Furman and the prosecution, claiming they were guilty of mishandling evidence and implicit bias; Furman was later found to have been recorded saying racial slurs, which he denied and lied about under oath on the witness stand.[8] Further, in a period of racial polarization due to the ongoing Rodney King trials, tensions were high among the Black community, as viewership called into question the neutrality of government officials.[9] While it is still up for debate whether or not the prosecution planted evidence, this trial is a clear example of how litigators' bias can impact a case's trajectory. For Simpson, the defense was able to use Furman’s biases to shift the focus of the case to delegitimizing the integrity of the prosecution rather than an objective examination of the evidence in connection to the murders themselves, thus proving that the context in which evidence is framed by attorneys (and their biases) can impact public perception and the interpretation of evidence.

Although the landmark Supreme Court case Daubert v. Merrell Dow Pharmaceuticals (1993) set the precedent of expert testimony standardization, an expert’s bias remains an unconsidered and influential factor. Scientific experts are often chosen and paid for by attorneys and their clients; they are not obligated to contribute the full scope of their knowledge but rather answer only what examiners ask or find relevant to their argument.[10] Fundamentally, the Daubert ruling established the standard for admitting expert testimony in the courtroom under the Federal Rules of Evidence (FRE), which states that evidence may be accepted based on reliable methods and principles.[11] This ruling effectively overturned the Frye v. United States, 293 F. 1013 (1923) precedent, which required that only evidence “generally accepted” by experts be admissible––thereby excluding new scientific research and discoveries. [12][13]Under the Daubert precedent, judges can validate if scientific expert testimony is admissible in the courtroom, determined by empirical facts and reasoning. [14]. Various considerations, including whether the evidence rested on scientific principles in addition to underlying and peer-reviewed techniques, are often noted when introducing expert testimony. Despite such considerations, there is a risk of cognitive bias, as scientific experts must determine whether evidence from a crime scene and a suspect are “sufficiently similar.” Evidence gathered from the crime and evidence gathered from potential suspects through forensic experts are obtained from separate locations and would never be identical. Thus, it is left to the examiner's discretion to determine whether a correlation exists; this often risks subjective evaluations.[15]

Under these circumstances, eliminating bias from the legal system may seem next to impossible; as Dr. Gleb Tsipursky from an Iowa Bar Association article shares, research on human behavioral science has shown that reasoning from attorneys in the legal system is “inherently flawed and vulnerable to both explicit and implicit biases.” [16]While it is true that bias is innate to human nature, there are steps legal practitioners and experts can pursue to eliminate the possibility of bias in their work. At the height of expert subjectivity, judges can appoint ‘neutral’ experts if they find the ones litigants provide insufficient in objective testimony. [17] Established in 2001 and expanded in 2004 by the American Association for the Advancement of Science, the Court Appointed Scientific Experts (C.A.S.E.) project serves as a liaison between trial judges and experts, helping the judiciary maintain neutrality through the acquisition of external experts; “Your assistance allowed me to offer to the parties a totally objective examination of the case by qualified and competent experts,” stated a judge from the district of Nebraska after using the C.A.S.E. program. [18][19]​​ Further, expert witnesses and attorneys can adopt ‘Line Sequential Unmasking,’ a practice in which experts only examine evidence in isolation of the target subject to minimize unnecessary information shared with experts that may subconsciously influence their interpretation of the evidence. [20] Through these measures, litigators and scientists can proactively work together to uphold a legal standard of neutrality.

Despite its limitations, when applied with the intent to truthfully and reliably clarify case events, science becomes a powerful tool that shapes legal precedent. In the case of the nationally recognized People v. Santana, Wise, McCray, Richardson, and Salaam (1990), five African American boys from New York City were wrongfully convicted of an assault against a Central Park jogger, Trisha Meili. [21] Upon arrest, the New York City police deprived the boys of food, drink, and sleep for more than twenty-four hours, coerced them into false confessions, and used inconsistent DNA samples to ultimately convict them of the crime. [22] In December of 2002, Justice Charles J. Tejada of the Supreme Court of the State of New York granted a motion to vacate their convictions as a result of newly discovered DNA evidence, in addition to a confession by Matias Reyes, the true perpetrator. [23] In the case of The Exonerated Five, though the justice system wrongfully convicted innocent litigants due to bias by legal practitioners and faulty evidence, their exoneration was a testimony to the more tremendous potential of the justice system when scientific evidence is used with objectivity and fairness.

Though attorneys and experts are human, it is their sworn duty to actively strive for impartiality amidst the risk of cognitive bias; while the task may be daunting, the law depends on continuous objectivity and fairness. Forensic evidence has been and will continue to be forefronted as the factual foundation for legal discourse, and only when it is used and handled with integrity can justice be fully achieved.

Bibliography

[1] Darcy, Oliver. 2024. “How OJ Simpson’s ‘trial of the century’ reshaped the national media and opened the door to Donald Trump’s presidency.” CNN. https://www.cnn.com/2024/04/12/media/oj-simpson-trial-reshaped-media-trump-presidency/index.html.

[2] Diamond, Shari Seidman, and Richard O. Lempert. “Introduction.” Daedalus 147, no. 4 (October 2018): 5–14. https://doi.org/10.1162/daed_x_00516.

[3] Giorgi, Marcela. n.d. “What are the Different Types of Scientific Evidence Used in Criminal Cases?” Adams, Luka, & Benton. Accessed March 10, 2025. https://www.adamsluka.com/what-are-the-different-types-of-scientific-evidence-used-in-crim.html.

[4] Albright, Thomas D., David Baltimore, Marie Mazza, Jennifer L. Mnookin, and David S. Tatel. "Science, Evidence, Law, and Justice." Proceedings of the National Academy of Sciences of the United States of America 120, no. 41 (2023): e2312529120. Accessed March 2, 2025. 6-7. https://doi.org/10.1073/pnas.2312529120.

[5] People v. Simpson, 35 Cal. 4th 1 (Cal. 2004)

[6] Jasanoff, Sheila. “The Eye of Everyman.” Social Studies of Science 28, no. 5–6 (October 1998): 724–26. https://doi.org/10.1177/030631298028005003.

[7] Jasanoff, Sheila. “The Eye of Everyman.” Social Studies of Science 28, no. 5–6 (October 1998): 724–26. https://doi.org/10.1177/030631298028005003.

[8] Dazio, Stefanie. “California Law Bars Ex-LAPD Officer Mark Fuhrman, Who Lied at OJ Simpson Trial, from Policing.” AP News, June 8, 2024. https://apnews.com/article/mark-fuhrman-decertified-oj-simpson-trial-3e3e691a5c6b5671dd8aedf06b96b444.

[9] Frank A. Bellis Jr., "When Private Interests Consume the Public Good: The OJ Simpson Case," Journal of Financial Crime 5, no. 1 (1997): 55-58

[10] Albright, Thomas D., David Baltimore, Marie Mazza, Jennifer L. Mnookin, and David S. Tatel. "Science, Evidence, Law, and Justice." Proceedings of the National Academy of Sciences of the United States of America 120, no. 41 (2023): e2312529120. Accessed March 2, 2025. 6. https://doi.org/10.1073/pnas.2312529120.

[11] Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993)

[12] Frye v. United States, 293 F. 1013 (1923)

[13] Daubert sets Standard for Court’s Scientific Method (Daubert V. Merrell Dow Pharmaceuticals, inc.. Accessed March 2, 2025. https://www.americanbar.org/groups/law_students/resources/on-demand/quimbee-daubert-v-merrell-dow-pharmaceuticals-inc/.

[14] Jasanoff, Sheila. “The Eye of Everyman.” Social Studies of Science 28, no. 5–6 (October 1998): 722–23. https://doi.org/10.1177/030631298028005003.

[15] Dror, Itiel E, Justice Bridget M McCormack, and Jules Epstein. Cognitive bias and its impact on expert witnesses and the ... Accessed March 2, 2025. https://law.temple.edu/wp-content/uploads/Cognitive-Bias-and-Its-Impact-on-Expert-Witnesses-and-the-Court.pdf.

[16] “Debiasing the Law: How Understanding Cognitive Biases Leads to a More Just Legal System.” The Iowa Lawyer Magazine. Accessed March 10, 2025. https://www.iowabar.org/?pg=IowaLawyerMagazine&pubAction=viewIssue&pubIssueID=33575&pubIssueItemID=195820.

[17] Jasanoff, Sheila. “The Eye of Everyman.” Social Studies of Science 28, no. 5–6 (October 1998): 722–722. https://doi.org/10.1177/030631298028005003.

[18] “Court Appointed Scientific Experts (Case).” American Association for the Advancement of Science (AAAS). Accessed March 10, 2025. https://www.aaas.org/programs/court-appointed-scientific-experts.

[19] “Case: Experience.” American Association for the Advancement of Science (AAAS). Accessed March 10, 2025. https://www.aaas.org/programs/court-appointed-scientific-experts/experience.

[20] Dror, Itiel E, Justice Bridget M McCormack, and Jules Epstein. Cognitive bias and its impact on expert witnesses and the ... Accessed March 2, 2025. https://law.temple.edu/wp-content/uploads/Cognitive-Bias-and-Its-Impact-on-Expert-Witnesses-and-the-Court.pdf.

[21] People v. Santana, Wise, McCray, Richardson, and Salaam, 175 A.D.2d 41 (N.Y. App. Div. 1992)

[22] Diaz, Jaclyn. “The Central Park 5 Are Suing Trump over Philly Debate Comments.” NPR, October 21, 2024. https://www.npr.org/2024/09/11/nx-s1-5108632/central-park-five-trump-debate.

[23] ​​“Conviction and Exoneration.” PBS. Accessed March 2, 2025. https://www.pbs.org/kenburns/the-central-park-five/conviction-and-exoneration.