Age-at-Death Estimation of Fetuses and Infants in Forensic Anthropology: A New "Coupling" Method to Detect Biases Due to Altered Growth Trajectories

Abstract

The coupling between maturation and growth in the age estimation of young individuals with altered growth processes was analyzed in this study, whereby the age was determined using a geometric morphometrics method. A medical sample comprising 223 fetuses and infants was used to establish the method. The pars basilaris shapes, quantified by elliptic Fourier analysis, were grouped into consensus stages to characterize the maturation process along increasing age groups. Each pars basilaris maturation stage was "coupled" to biometry by defining an associated femur length range. The method was tested on a validation sample of 42 normal individuals and a pathological sample of 114 individuals whose pathologies were medically assessed. Couplings were present in 90.48% of the normal sample and 77.19% of the pathological sample. The method was able to detect "uncoupling" (i.e., possibly altered growth) in more than 22.8% of samples, even if there was no visible traces of pathology on bones in most cases. In conclusion, experts should be warned that living conditions may cause alterations in the development of young individuals in terms of uncoupling, and that the age-at-death estimation based on long bone biometry could be biased. In a forensic context, when age has been estimated in cases where uncoupling is present, experts should be careful to take potential inaccuracies into account when forming their conclusions.

Keywords: age estimation; femur length; forensic anthropology; geometric morphometrics; inverse Fourier transform; pars basilaris shape.

Figure 1

Age (in weeks) and sex distribution of the learning sample (A) comprising 223 individuals and the validation sample (B) comprising 42 individuals. Age (in weeks) and sex distribution of the pathological sample (C) comprising 114 individuals.

Figure 1

Age (in weeks) and sex distribution of the learning sample (A) comprising 223 individuals and the validation sample (B) comprising 42 individuals. Age (in weeks) and sex distribution of the pathological sample (C) comprising 114 individuals.

Figure 2

Outline reconstructions of the pars basilaris (dark outline): harmonics 1, 5, 10, and 14. Gray shapes represent the reconstruction of the pars basilaris with the maximum number of harmonics (74 in this study).

Figure 3

Maturation and growth criteria by stage and age group (in weeks).

Figure 4

Chart summarizing the subgroups and the detailed pathological conditions for individuals in the medical imaging sample with uncoupling. IUGR = intrauterine growth retardation.