This dissertation examines the possibility and methodology of performing sex estimations in individuals younger than the cultural and legal definition of adulthood, 18 years, falling into the subadult biological profile in which skeletal development and maturation have not yet been completed.
This paper reports on an investigation of the ontogenetic trajectories of the most commonly used traits for adult sex estimation, to allow for the determination of their true capacity to estimate sex in subadults younger than 18 years old. The research methodology included collecting data from a large sample of American individuals, 386 males and 239 females, between the ages of eight and 20 years, from the Subadult Virtual Anthropology Database. The research had three specific aims: to determine the age at which sex traits of the skull and pelvis become dimorphic and reach full expression, and quantify the predictive power of each trait throughout ontogeny; to determine when during maturation the skull and pelvic sex traits become dimorphic using various skeletal maturity indicators associated with puberty to serve as a guide for forensic practitioners in deciding if an immature individual is sufficiently mature for a sex estimate to be made, without relying on age; and lastly, to develop sex classification models for the creation of a new two-step method for subadult sex estimation that is based on ontogeny through incorporating skeletal maturity indicators associated with puberty and modified skull and pelvic sex trait descriptions and scoring procedures specifically for use with subadults. Results are discussed in detail, indicating that most skull and pelvic traits express dimorphism prior to adulthood; skeletal maturity indictors associated with puberty provided a valid way to estimate maturity status; and subadult sex estimation can be as accurate as adult sex estimation when using appropriate samples and taking an ontogenetic approach. The method developed through this project, The Ontogenetic Subadult Sex Estimation (OnSEt) System, is freely available as a graphical user interface.