Dr. Killen received an M.D. (1980) and Ph.D. (Pathology)(1985) from the University of Washington, Seattle. After a year of residency in Internal Medicine, Dr. Killen completed residency training in Anatomic Pathology at the University of Washington, Seattle Hospitals, followed by Post-Doctoral Fellowship training at the Laboratory of Developmental Biology and Anomalies, at the National Institutes of Health. He served as Acting Director of the Renal Biopsy Service and Instructor in the Department of Pathology at the University of Washington, Seattle prior to joining the faculty of the Department of Pathology at the University of Michigan as Assistant Professor in 1987. In 1994, Dr. Killen was promoted to the rank of Associate Professor and in 2002, he assumed the Directorship of the Electron Microscopy Laboratory. Dr. Killen is board certified in Anatomic Pathology.

 Dr. Killen's research interests include basement membranes are specialized extracellular matrices which provide a substratum for cell attachment and thereby influence the differentiated phenotype of cells.