From my source
Most studies support a link between adult criminality and testosterone. Nearly all studies of juvenile delinquency and testosterone are not significant. Most studies have also found testosterone to be associated with behaviors or personality traits linked with criminality such as antisocial behavior and alcoholism. Many studies have also been done on the relationship between more general aggressive behavior and feelings and testosterone. About half the studies have found a relationship and about half no relationship.[73] Studies have also found that testosterone facilitates aggression by modulating vasopressin receptors in the hypothalamus.[74]
There are two theories on the role of testosterone in aggression and competition.[75] The first one is the challenge hypothesis which states that testosterone would increase during puberty, thus facilitating reproductive and competitive behavior which would include aggression.[75] It is therefore the challenge of competition among males of the species that facilitates aggression and violence.[75] Studies conducted have found direct correlation between testosterone and dominance, especially among the most violent criminals in prison who had the highest testosterone levels.[75] The same research also found fathers (those outside competitive environments) had the lowest testosterone levels compared to other males.[75]
The second theory is similar and is known as “evolutionary neuroandrogenic (ENA) theory of male aggression”.[76][77] Testosterone and other androgens have evolved to masculinize a brain in order to be competitive even to the point of risking harm to the person and others. By doing so, individuals with masculinized brains as a result of pre-natal and adult life testosterone and androgens enhance their resource acquiring abilities in order to survive, attract and copulate with mates as much as possible.[76] The masculinization of the brain is not just mediated by testosterone levels at the adult stage, but also testosterone exposure in the womb as a fetus. Higher pre-natal testosterone indicated by a low digit ratio as well as adult testosterone levels increased risk of fouls or aggression among male players in a soccer game.[78] Studies have also found higher pre-natal testosterone or lower digit ratio to be correlated with higher aggression in males.[79][80][81][82][83]
The relationship between testosterone and aggression may also function indirectly, as it has been proposed that testosterone does not amplify tendencies towards aggression but rather amplifies whatever tendencies will allow an individual to maintain social status when challenged.