DNA analysts' experiences with human factors: A quantitative and qualitative snapshot

DNA analysis can play a crucial role in rightful and wrongful convictions. However, forensic experts' methods may be influenced by human factors, including cognitive bias. Examiners' efforts to mitigate such bias can play a role in their courtroom testimony. There is little recent research on real-world DNA examiners' actual experiences with cognitive bias and expert testimony, nor their perceived training needs. To address this gap, we surveyed a national sample of forensic DNA analysts using Likert-scale and open-ended questions about cognitive bias, courtroom testimony, and related research and training needs. A total of 84 examiners responded to at least one question about bias or expert testimony. On average, examiners reported receiving biasing-contextual information about the investigation prior to their examination in 37% of their cases, with the most common types being eyewitness identifications and confession evidence. [Correction added on 19 May 2025, after first online publication: The preceding sentence has been revised in this version.] The majority of examiners (60%) reported that their laboratories have policies in place to decrease cognitive bias, and almost all examiners (90%) reported having provided expert testimony. Experts in our sample generally believed their testimony was understandable to jurors but pointed out the need for training in select areas, such as effectively communicating statistics in court, answering hypothetical questions on the stand, and communicating findings effectively in court. Our findings demonstrate that laboratories are generally in line with the National Academy of Sciences recommendations for policies to decrease cognitive bias, but there is room for improvement in limiting DNA analysts' exposure to biasing contextual information and meeting their human factors training needs.