Toward DNA-Based facial composites: Preliminary results and validation

The potential of constructing useful DNA-based facial composites is forensically of great interest. Given the significant identity information coded in the human face, these predictions could help investigations out of an impasse. Although there is substantial evidence that much of the total variation in facial features is genetically mediated, the discovery of which genes and gene variants underlie normal facial variation has been hampered primarily by the multipartite nature of facial variation. Traditionally, such physical complexity is simplified by simple scalar measurements defined a priori, such as nose or mouth width or alternatively using dimensionality reduction techniques such as principal component analysis, where each principal coordinate is then treated as a scalar trait; however, as shown in previous and related work, a more impartial and systematic approach to modeling facial morphology is available and can facilitate both the gene discovery steps, as the authors recently showed, and DNA-based facial composite construction, as they show in the current project. Overall, The results are preliminary but promising, especially considering the limited amount of genetic information about the face contained in the 24 SNPs involved in the study. The authors first used genomic ancestry and sex to create a base-face, which is simply an average sex and ancestry matched face. Subsequently, the effects of 24 individual SNPs that have been shown to have significant effects on facial variation were overlaid on the base-face forming the predicted-face in a process akin to a photomontage or image blending. They next evaluated the accuracy of predicted faces using cross-validation. Physical accuracy of the facial predictions either locally in particular parts of the face or in terms of overall similarity was mainly determined by sex and genomic ancestry. The SNP-effects maintain the physical accuracy while significantly increasing the distinctiveness of the facial predictions, which would be expected to reduce false positives in perceptual identification tasks. This approach can incorporate additional SNPs as these are discovered and their effects documented. In this context, the authors discuss three main avenues of research: expanding knowledge of the genetic architecture of facial morphology, improving the predictive modeling of facial morphology by exploring and incorporating alternative prediction models, and increasing the value of the results through the weighted encoding of physical measurements in terms of human perception of faces. (Publisher abstract modified)