Independent Validation of Population-Specific Equations for Sex and Stature Estimation from the Humerus in Northeastern Thailand

Background/Objective: Accurate biological profile estimation from skeletal remains is fundamental to forensic identification. While the humerus demonstrates considerable sexual dimorphism, population-specific validation data for Thai populations remain limited. This study aimed to develop and independently validate population-specific equations for sex and stature estimation from humeral measurements in Northeastern Thai populations. Methods: This cross-sectional study examined 300 adult humeri (150 male, 150 female) from the Khon Kaen University skeletal collection. Four osteometric measurements (maximum length, midshaft circumference, epicondylar breadth, superior–inferior head diameter) and weight were recorded. The sample was randomly divided into development (n = 200) and validation (n = 100) datasets. Logistic regression for sex estimation and linear regression for stature estimation were developed using stepwise selection. Results: Sex classification achieved 93.5% accuracy in development and 93.0% in independent validation. The optimal model incorporated midshaft circumference, superior–inferior head diameter, and weight, with an area under the curve of 0.977 (95% CI: 0.953–1.000), sensitivity 90.0%, specificity 96.0%, and Cohen’s kappa 0.86. Stature estimation demonstrated a correlation coefficient of 0.81 with a mean absolute error of 4.36 cm (2.74% of the mean stature). Independent validation confirmed minimal performance deterioration for both models. Conclusions: These independently validated, population-specific equations provide accurate and reliable methods for biological profile estimation in Northeastern Thai forensic contexts. The rigorous validation framework supports confident operational application and provides a methodological model for developing regional forensic standards.