A Bayesian approach to Suchey-Brooks age estimation from the pubic symphysis using modern American samples

A critical component of the biological profile involves accurate estimation of the age-at-death of the decedent(s). While bias, inaccuracy, and population specificity have plagued age estimation methods, these issues are minimized by Bayesian statistics. Our primary analysis generated ages of transition from the published Suchey-Brooks pubic symphysis dataset and coupled them with informative priors derived from two modern American forensic samples (Forensic Data Bank [FDB] and Forensic Anthropology Database for Assessing Methods Accuracy [FADAMA]) to test the accuracy of Bayesian analysis against the original method. Exact binomial tests assessed the accuracy of the generated age ranges; realized accuracies and bias are reported for final age ranges at various coverages. In a second analysis, the Bayesian Suchey-Brooks parameters and original, non-Bayesian age ranges were also applied to FADAMA. In the primary analyses, the Bayesian approach improved age estimates over traditional ranges, especially for females. Highest posterior density ranges at 95% provided realized accuracies on a holdout sample between 93% and 96% with extremely low bias for most phases. We provide lookup tables with Bayesian age ranges for various coverages. In the second analysis, realized accuracies were slightly higher in the non-Bayesian approach for both sexes (86%-92% vs. 83%-91%), due to lower precision and likely practitioner bias in aging forensic cases. The popularity of the Suchey-Brooks pubic symphysis aging method in modern forensic casework necessitates the use of the Bayesian approach and we encourage practitioners to utilize the lookup tables for forensic casework in the United States.