His research focuses on the clinical neuroscience of major mental illnesses, especially criminal psychopathy, substance abuse, and psychotic disorders. Over the course of his research, he has produced a number of tests and software packages to aid research in the field. He recently edited a book on psychopathy and law and has published over 80 articles exploring the neuroscience of psychopathy and schizophrenia. His work also includes studies of the related phenomena of empathy, impulsivity, and inhibition.