Human Factors is a cross-disciplinary field of research that intersect Psychology, Engineering and Kinesiology. To be effective, the Human Factors Expert Witness needs to be well-versed in several disciplines, with Cognitive Science being a prominent one.
Nowadays, psychological factors play a primary role in determining how the human operator interact with automotive and manufacturing systems. As a result, the HF expert needs to have a comprehensive understanding of human cognition.
For example, in a recent legal dispute that I was hired on, I was asked to provide my expert opinion about the role that task-switching (a well-known cognitive phenomenon whereby the cost of switching from one task to another adds to the overall cognitive workload) had on the overall distraction of the vehicle operator.
While many Human Factors Expert Witnesses have a strong background in Kinesiology or Engineering, they often lack a solid understanding of human cognition, which, as evidenced by recent literature, is necessary to explain the role that human error plays in the automotive or manufacturing workplace.
References
Biondi, F., Alvarez, I., & Jeong, K. A. (2019). Human–vehicle cooperation in automated driving: A multidisciplinary review and appraisal. International Journal of Human–Computer Interaction, 35(11), 932-946.
Canadian Centre for Occupational Health and Safety (n.d.) Psychosocial Factors.