Psychological and psychiatric theories of criminal behaviour emphasise individual propensities and characteristics in explanations of criminality. Whether the emphasis is on conditioned behaviour, the development of parental attachment, or the psychoanalytic structure of the human personality, these approaches see the wellsprings of human motivation, desire, and behavioural choice as being firmly rooted in the personality.
Some of the earliest positivists were convinced that criminal behaviour was a result of genetic abnormality. Lombroso advanced the notion of atavism, which stated criminals represented a savage, earlier form of humankind. Lombroso compiled a list of physical features that were associated with criminals, which included protruding eyes, long arms, tattoos and large jaws. He tested convicts and those who had 5 or more of these atavisms were deemed to be born criminals. However his research was based on male criminals in a Sicilian jail which was inadequate as a control group as it had an overrepresentation of Sicilians who naturally demonstrated several of Lombrosos atavisms.
Sheldons somatic typology theory was based on a large sample of males in rehabilitation institutions. He listed three major somatypes (or body types); endomorphs: obese, soft, and rounded people who were fun loving and sociable;
mesomorphs: muscular, athletic people who were assertive, vigorous, and bold; ectomorphs: tall, thin, with a well developed brain who were introverted, sensitive, and nervous. Sheldon thought that mesomorphs were most likely to become criminals. However unrepresentative samples were used and he may have been confusing causation with correlation - just because there is an association between body type and deviant behaviour doesn't mean that the body type/biology caused the deviant behaviour. Also neither of these theories take into account female crime.
…
