This study uses the celebrated American trial of Charles Guiteau, who assassinated President James A. Garfield in 1881, to explore attitudes towards insanity and criminal responsibility in the the late-19th century. The author reconstructs the courtroom battle waged by 24 expert witnesses who represented the two major schools of psychiatric thought of the generation immediately preceding Freud. Although the role of genetics in behaviour was widely accepted, these psychiatrists debated whether heredity had predisposed Guiteau to assassinate Garfield. Rosenberg's account allows the reader to consider one of the earliest cases in the controversy over the criminal responsibility of the insane, a debate that has continued through to modern times.