Abstract
The study of facial growth is explored in many fields of science, including anatomy, genetics, and forensics. In the field of forensics, it acts as a valuable tool for combating child pornography. The present research proposes a new method, based on relative measurements and fixed references of the human face—specifically considering measurements of the diameter of the iris (iris ratio)—for the analysis of facial growth in association with age in children and sub-adults. The experimental sample consisted of digital photographs of 1000 Brazilian subjects, aged between 6 and 22 years, distributed equally by sex and divided into five specific age groups (6, 10, 14, 18, and 22 year olds ± one month). The software package SAFF-2D® (Forensic Facial Analysis System, Brazilian Federal Police, Brazil) was used for positioning 11 landmarks on the images. Ten measurements were calculated and used as fixed references to evaluate the growth of the other measurements for each age group, as well the accumulated growth (6–22 years old). The Intraclass Correlation Coefficient (ICC) was applied for the evaluation of intra-examiner and inter-examiner reliability within a specific set of images. Pearson’s Correlation Coefficient was used to assess the association between each measurement taken and the respective age groups. ANOVA and Post-hoc Tukey tests were used to search for statistical differences between the age groups. The outcomes indicated that facial structures grow with different timing in children and adolescents. Moreover, the growth allometry expressed in this study may be used to understand what structures have more or less proportional variation in function for the age ranges studied. The diameter of the iris was found to be the most stable measurement compared to the others and represented the best cephalometric measurement as a fixed reference for facial growth ratios (or indices). The method described shows promising potential for forensic applications, especially as part of the armamentarium against crimes involving child pornography and child abuse.
Highlights
The human face does not grow homogenously over time
The Intraclass Correlation Coefficient revealed excellent outcomes for the landmarking performed in the intra- and interexaminer reliability tests, which were performed prior to and during the research project (ICC > 0.90; p < 0.001)
Average Relative Growth (ARG) reached the lowest values in all age groups in comparison to the other measurements
Summary
The human face does not grow homogenously over time. Each of the many facial structures develops in different dimensions and directions [1, 2]. The facial anatomy reaches different proportions depending on age [1, 3, 4]. This phenomenon, known as allometry, is the reason why a child’s face does not correspond to a smaller version of an adult’s face. Nowadays, alternative applications of craniofacial morphology, such as in the scope of forensic sciences, has received major attention In this regard, forensic studies were developed in the last decade to investigate facial growth as an anthropometric tool for age estimation procedures in cases involving child pornography [16, 17]
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