The skull and humerus in the determination of sex: Reliability of discriminant function equations

Sex determination plays a crucial role in the identification of human remains as it narrows the possibility for identification by 50%. The purpose of this study is to test the validity of five discriminant function equations, with accuracies of 80% and higher, that have been derived by Steyn and Işcan [M. Steyn, M.Y. Işcan, Sexual dimorphism in the crania and mandibles of South African Whites, Forensic Sci. Int. 98 (1998) 9-16; M. Steyn, M.Y. Işcan, Osteometric variation in the humerus: sexual dimorphism in South Africans, Forensic Sci. Int. 106 (1999) 77-85] for the skull and humerus of South Africans of European Descent (SAED). These equations were tested on different regional populations of SAED within South Africa. While the validity of some of the discriminant functions has been assessed by the authors who derived them, no other previous independent study has been carried out to assess the reliability of these equations. In addition, these equations have not been tested on skeletons located outside the Gauteng province. The study sample consisted of 230 skulls and 264 humeri of SAED obtained from four South African skeletal collections: Raymond A. Dart Collection of Human Skeletons (Johannesburg); Pretoria Bone Collection; Cape Town Skeletal Collection; and the Osteology Archive Student Collection (Stellenbosch). A total of 14 measurements (12 cranial and 2 humeral) were taken on these skeletal elements. The observed accuracies from the present study (72.0-95.5%), with the exception of one sample's accuracy, compared well with the original classification rates (80.2-92.5%) for most of the functions thereby confirming the validity of the discriminant function equations for sex determination for the skull and humerus of SAED, for SAED in all regions of South Africa.