Developmental asymmetry of the clavicles and third molars and its implications for forensic age estimation

Age estimations are relevant for pre-trial detention and sentencing in criminal cases and as part of the evaluation in asylum processes to protect the rights and privileges of minors. No method can determine an exact chronological age due to individual variations in biological development. Current techniques assess skeletal or dental development and compare to reference populations. A key question is whether both sides of a body part need imaging, especially when asymmetric development occurs. This study evaluates whether bilateral imaging of the clavicles and third molars is necessary or if unilateral imaging suffices. We retrospectively analyzed clinical and radiological data from patients who underwent CT scans at Karolinska University Hospital, along with third molar data from studies using plain radiographs to assess development in relation to chronological age. The primary aim of this study is to examine the frequency of asymmetrical maturation in the medial clavicle and third molar in males and in females. The secondary aim was to examine how asymmetry influences age estimation in medico-legal contexts. To mitigate potential bias from relying on a single-reviewer assessment, we introduced a predefined level of misclassification into our model. Our findings show a strong correlation between right and left clavicle development (ρ = 0.871 (males) and ρ = 0.854 (females)) and near-perfect correlation (ρ = 0.980 (males) and ρ = 0.975 (females)) for third molars in both sexes. Asymmetrical development was found in approximately 23% (clavicle) and 13% (third molar) of males, and 20% and 17% of females, respectively. We recommend bilateral clavicle assessment to capture developmental variation and improve accuracy. For third molars, using the side with the most mature development in males and the least mature side in females enhances accuracy around the 18-year threshold.