Throughout his career, he has worked with several children's and adult hospitals and medical centers. He has worked in the areas of acute and chronic illness, neonatal intensive care, burns and trauma, general pediatrics and surgery. He has consulted with child protective service agencies, school districts, the Social Security Administration's Disability Determination Services Administration, and has performed forensic evaluations in personal injury, competency, and educational due process arenas. Dr. Nicholls has been on the clinical faculty of several major universities and graduate programs.