In many ways the excuse-giving system of medicine parallels the excuse-giving system in law. A diagnosis of medical illness or impairment can excuse a patient from responsibility for substandard or deviant conduct. Perceiving crime as an illness is one way to deal with criminals. The article advocates open-ended sentences and discusses the advantages of using a medical model of excuse-giving in the criminal justice system, focusing on the need to consider differences in individual capacities in determining blame and punishment. The article points out that it is merely a matter of time before societies will use biological methods for treating crime by altering brain chemistry. The future medical model for criminology, to be effective, must place responsibility for improvement on the perpetrator, encouraging him to use all of his capacities to prevent further criminal acts. 61 footnotes.