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

Area of Science:

• Forensic Anthropology
• Developmental Biology

Background:

• Dental development is a key indicator for age estimation in forensic contexts.
• Legal frameworks often rely on age thresholds, necessitating accurate age assessment methods.

Purpose of the Study:

• To evaluate the utility of first and second mandibular molar development in assessing the minimum age of criminal responsibility.
• To investigate the reliability of dental evidence for legal age determination.

Main Methods:

• Utilized a large sample (N = 2,676) of individuals.
• Applied a bivariate ordered probit model to dental scores using the Moorrees et al. (1963) system with an added crypt-absent/present stage.
• Employed 10-fold cross-validation and Bayesian analysis with a normal prior centered on the age threshold.

Main Results:

• Bivariate models produced unbiased age estimates but showed heteroskedasticity.
• Achieving robust posterior odds for age threshold determination required assuming an unreasonably high standard deviation of age.
• Dental developmental evidence from first and second molars proved to be of limited use.

Conclusions:

• First and second mandibular molar development is not a sufficiently precise tool for establishing the minimum age of criminal responsibility.
• The variability in third molar development further complicates dental evidence for determining the age of majority (18 years).