Medical men are often called upon to give evidence as to the mental condition of an individual, charged with crime, at the time of committing the crime. They are also expected to give an opinion as to whether by reason of insanity the accused was incapable of knowing the nature and consequences of his act, or did not know that what he was doing was either wrong or contrary to law. The question is frequently one of life and death for the accused, and therefore it is very necessary that medical men should understand the inner working of a criminal's mind before they venture an opinion regarding his mental condition. In India we have hitherto depended for our guidance on books written by learned authors who base their conclusions on conditions prevailing in their own countries, and cannot be expected to know the conditions of Indian life. I feel the time has come when we should begin to collect first-hand information regarding our criminals from our own observations. I am afraid very little work has been done in this field in India, and it is time that we compare our results with those obtained in the West. It is with this object that I venture to submit this paper, so that it may stimulate others in India also to work on these lines.