Pitfalls at the root of facial assessment on photographs: a quantitative study of accuracy in positioning facial landmarks

Abstract

In the last years, facial analysis has gained great interest also for forensic anthropology. The application of facial landmarks may bring about relevant advantages for the analysis of 2D images by measuring distances and extracting quantitative indices. However, this is a complex task which depends upon the variability in positioning facial landmarks. In addition, literature provides only general indications concerning the reliability in positioning facial landmarks on photographic material, and no study is available concerning the specific errors which may be encountered in such an operation. The aim of this study is to analyze the inter- and intra-observer error in defining facial landmarks on photographs by using a software specifically developed for this purpose. Twenty-four operators were requested to define 22 facial landmarks on frontal view photographs and 11 on lateral view images; in addition, three operators repeated the procedure on the same photographs 20 times (at distance of 24 h). In the frontal view, the landmarks with less dispersion were the pupil, cheilion, endocanthion, and stomion (sto), and the landmarks with the highest dispersion were gonion, zygion, frontotemporale, tragion, and selion (se). In the lateral view, the landmarks with the least dispersion were se, pronasale, subnasale, and sto, whereas landmarks with the highest dispersion were gnathion, pogonion, and tragion. Results confirm that few anatomical points can be defined with the highest accuracy and show the importance of the preliminary investigation of reliability in positioning facial landmarks.

Juvenile age estimation from facial images

“…The availability of child pornographic images has grown exponentially with the development of the internet resulting in millions of images of CSA, which are shared and downloaded online (4,7,8). Consequently, there has been a rise in the number of cases in which an expert has been called upon to give an age assessment from a photograph of alleged CSA (4,5).…”

“…Visual assessment of age from pornographic images has been based on the evaluation of the Tanner stages of development and other sexual maturity indicators, with the face also suggested to be an important feature for analysis (8,12). However, studies have shown that age estimation from secondary sexual characteristics is inaccurate, with wide variability in the choice of features believed to be most important in age assessment (8).…”

“…However, studies have shown that age estimation from secondary sexual characteristics is inaccurate, with wide variability in the choice of features believed to be most important in age assessment (8). Growth and sexual maturation can be affected by many factors such as environmental factors, obesity and malnutrition, population differences and even individual biology can influence the rate and timing of sexual maturation (4,5,13).…”

“…Moreover, the facial landmarks from which measurements are taken may not be readily visible in lower quality images. The placement of facial landmarks have already been shown to display varying degrees of interobserver error, even when placed on high quality images (8).…”

Modeling Skull-Face Anatomical/Morphological Correspondence for Craniofacial Superimposition-Based Identification

“…However, despite some authors considering this technique as a valid identification method [6], [8], [9], [20], many others only regard CFS as a tool for the exclusion method [21]- [23]. The fact that two different objects have to be compared implies a number of sources of uncertainty, making CFS identification a subjective technique, highly dependent on the forensic anthropologist's experience and knowledge: acquisition parameters of the photographs [24], [25], mandible articulation, landmark location imprecision [26], soft tissue depth variability [15], and ultimately morphological comparison.…”