Error and bias in forensic behavioral science

A crisis is brewing in scientific psychology and forensic science. This concerns the overall reliability of all psychological science (more on this later) and the quality of expert evidence and testimony in courts of law, regardless of the expert’s discipline (yes, even including the supposedly hard stuff, like DNA analysis).

The consensus: alarmingly poor. This is the opinion of National Academy of Sciences’ National Research Council Report, “Strengthening Forensic Science in the United States: A Path Forward.”
“The focus has shifted to include the evaluation of methods and techniques rather than simply the expert’s interpretation of the results” (Christensen et al, 2014, p. 123).

The concern here is the quality of expert testimony in high stakes situations where the reliability of judicial decision-making, indeed the very integrity of the legal system is raised.

If experts are doing due diligence in enhancing the quality of their forensic work, including the thoroughness and integrity of their methods and opinions, two recent articles, one a major contribution, address these issues.

First, the article by Christensen et al (2014), Error and its meaning in forensic science. Journal of Forensic Science, 59, 1, 123-126, addresses the fundamental question of error.

What is error? Is error common, inevitable, correctable, or avoidable? Are you aware that you even have an error rate in your decision-making?

In forensic mental health assessments, research shows that reliability is poor; hence, heightened error rates.

What is error? Error means that you made the wrong decision, that your opinions are flawed or incorrect based procedural and/or methodological deficiencies…or bias.

What is bias?

A very powerful article by Neal & Grisso (2014) provides a conceptual foundation and call for research on bias in forensic mental health evaluations, addressing conscious and unconscious biases, including common cognitive heuristics utilized by all human beings, including scientists, lawyers, judges, and juries.

They provide clear and concise definitions and conceptual issues for addressing the conceptual foundations of bias. This work in rooted in the seminal, 1974 article by Tversky & Kahneman, which opened the whole era of cognitive heuristics and the role of bias in the intuitive judgment of probability under conditions of uncertainty.

Hard going in the read, but valuable in the payoff.


Neal, T., & Grisso, T. (2014). The cognitive underpinnings of bias in forensic mental health evaluations. Psychology, Public Policy, and the Law, on line publication.

Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185, 27 September 1974, 1124-1131.


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