Prior Probabilities and the Age Threshold Problem: First and Second Molar Development

Dental development has been used to assess whether an individual may be below or above age that serves as a legal threshold. This study of the first and second mandibular molars from large sample individuals (N = 2,676) examine threshold for minimum criminal responsibility. A bivariate ordered probit model was applied dental scores following Moorrees et al. (1963) system, with addition crypt-absent/present stage. Then 10-fold cross-validation within each sexes showed models produce unbiased estimates but are heteroskedastic (with increasing spread against actual age). To address problem, normal prior centered on is assumed, product likelihood integrated up again starting at The ratio these two integrals Bayes factor, which because symmetric around threshold, can also interpreted posterior odds over versus under It necessary assume unreasonably high standard deviation in achieve were well “evens.” These results indicate developmental evidence limited use examining question As third molar more variable its than molars, regarding majority (generally 18 years) remains problematic.