People of all ages and ethnicities implicitly use others’ facial characteristics to evaluate their personalities. The field of person perception has identified several mechanisms through which one’s facial appearance may be associated with one’s behavior. For example, a person with an untrustworthy-looking face may elicit negative reactions from social partners, which may then cause the person to engage in more delinquency than they otherwise would have (expectancy effects), with negative outcomes for both the actor and those affected by their delinquent behavior. Alternatively, engagement in delinquency may cause a person to develop an untrustworthy appearance (a Dorian Gray effect). Such degradations in facial trustworthiness may in combination with expectancy effects interfere with desistence of delinquency during early adulthood or disadvantage persons who have desisted antisocial behavior. Thus, it is paramount to understand and interrupt both processes across development in order to reduce incidence of delinquency and encourage desistence. Yet the investigation of facial trustworthiness has rarely been generalized to a developmental context. The present project examined both the target of interpersonal perceptions (Study 1) and the processes that lead perceivers to behave differently toward those targets (Study 2). Study 1 leveraged methods from developmental psychology to follow a sample of 206 at risk boys from ages 13 to 38. This was the first study to chart the development of facial trustworthiness across adolescence and into adulthood. Initial levels of facial trustworthiness at age 13 predicted slower escalation in delinquency during adolescence and faster declines in delinquency during adulthood (expectancy effects), and initial levels of delinquency at age 13 predicted more rapid degradations in facial trustworthiness across adolescence (Dorian Gray effects). Study 2 utilized methods from experimental psychology to investigate the extent to which ambiguous behavioral information may intensify the effect of facial trustworthiness on perceivers’ evaluations, a process that may contribute to expectancy effects. However, Study 2 failed to replicate an effect of facial trustworthiness on perceivers’ evaluations of targets, thus, findings were equivocal regarding the primary hypothesis. It is the thesis of this project that 1) highlighting experiences of the perceiver and the target, and 2) utilizing methods from developmental and experimental psychology, are both necessary to understand the broader implications of person perception research.