Bias in Forensic Science

Bias has been a subject of concern in forensic science for the past few decades. Bias is a psychological phenomenon in which irrelevant factors influence someone’s perception, memory, interpretation, or conclusions. Like with other scientific fields, there is concern that bias may affect the work of forensic scientists and therefore make forensic work less reliable. Part of this concern is due to the potential for bias to skew a forensic scientist’s conclusions away from the ground truth of the case. Another part is that a forensic scientist should form their conclusions based only on the evidence they are tasked with analyzing and information relevant to its analysis. While there has been some resistance from within the forensic science field to the idea that forensic scientists can be biased, some cases and forensic scientists have demonstrated how irrelevant factors can influence forensic scientists during their analysis. For example, in the Brandon Mayfield case, bias led to FBI fingerprint analysts working backwards in their comparisons from Mayfield’s reference fingerprints to evidence fingerprints and falsely identifying evidence fingerprints from the Madrid bombing case as coming from Mayfield. Studies, some of which will be discussed in this thesis, have demonstrated bias impacting not just fingerprint analysis but also evidence collection at the crime scene, forensic anthropology, DNA analysis, toxicology, forensic pathology, forensic psychiatry, digital forensics, and other domains. Psychological research indicates that bias arises from how the human brain functions. However, researchers have also suggested ways to potentially reduce the impact of bias on forensic science work, which largely focus on restricting the case information available to forensic scientists working on the case, such as blinding procedures, linear sequential unmasking, the use of case managers, and evidence lineups. Further research will be important going forward to better understand how bias affects forensic science and how to combat it. Bias will have the potential to impact the analysis of evidence as long as human beings are involved in that analysis, but research from forensic scientists and psychologists can help establish methods of minimizing the effects of bias and improve the reliability of forensic science.