Evaluation of third molar maturity index (I3M) in assessing the legal age of subjects in an Indian Goan population

India affords special laws and exemptions to minors under the criminal, marriage, labour and administrative laws. Many perpetrators claim to be a minor in the hope of a lenient trial and verdict. The authorities often rely upon forensic experts to provide evidence-based reports. The third molar can be relied upon in the assessment of legal age as it continues developing into the early twenties. The method established by Cameriere et al in 2008 provides an objective method for the accurate evaluation of legal age. Our study was designed to analyze and validate the efficacy of Third Molar Maturity index (I3M) in an Indian Goan population and compare it to published literature. 542 panoramic radiographs of subjects aged between 14 and 24 years were evaluated. The chronologic age increased as I3M reduced. There was no evidence of sexual dimorphism in third molar development across various I3M classes (p>0.05). Receiver Operator Characteristic Curve was plotted for males and females which showed an Area Under Curve of 0.95 (95% CI, 0.92-0.97) and 0.93 (95% CI, 0.90-0.96) respectively. 2x2 contingency tables were used to test the performance of various I3M cut-off values ranging from I3M=0.02 to 0.14. I3M = 0.08 showed the most promising results for the assessment of legal age. Our study achieved a high degree of accurate classification of 0.90 and 0.88 for males and females respectively. Results demonstrate a sensitivity of 0.899 and 0.854 and specificity of 0.90 and 0.93 for males and females respectively. The positive likelihood ratios were 9.88 and 12.44 while negative likelihood ratio was 0.11 and 0.15 for males and females respectively. A favourable Bayes Post Test Probability of 0.95 was noted for both males and females. These results allow us to strongly recommend the use of I3M for the assessment of legal age in an Indian Goan population.