The Use of Forensic DNA Phenotyping in Predicting Appearance and Biogeographic Ancestry

Abstract

Background: Persons whose identifying DNA profile (STR profile) is not yet known to the ingvestigating authorities cannot be identified by standard forensic DNA analysis (STR profiling) as it is now practiced. In view of the current public debate, particularly in Germany, on the legalization of so-called forensic DNA phenotyping, we present its scientific basis, societal aspects, and forensic applications and describe the analytic techniques that are now available.

Methods: This review is based on pertinent publications that were retrieved by a selective search in PubMed and in public media, and on the authors' own research.

Results: Forensically validated DNA test systems are available for the categorization of eye, hair, and skin color and the inference of continental biogeographic ancestry. As for statistical measures of test accuracy, the AUC (area under the curve) values lie in the range 0.74-0.99 for eye color, 0.64-0.94 for hair color, and 0.72-0.99 for skin color, depending on the predictive model and color category used.The corre- sponding positive predictive values (PPV) are lower. Empirical social-scientific research on forensic DNA phenotyping has shown that preserving privacy and protecting against discrimination are major ethical and regulatory considerations.

Conclusion: All three methods of forensic DNA phenotyping-the predition of exter- nally visible characteristics, biogeographic ancestry, and the estimation of age from crime scene DNA-require a proper regulatory framework and should be used in conjunction with each other. Before forensic DNA phenotyping can be implemented in forensic practice, steps must be taken to minimize the risks of violation of privacy scrimination and to ensure that these methods are used transpar- ently and proportionately.

Figure

Illustration of individual test results from DNA-based prediction of eye, hair, and skin color. These are illustrative examples of six test subjects who were chosen for their diverse eye, skin, and hair color phenotypes, as shown in the photographs. A DNA sample from each subject was analyzed with the HIrisPlex-S DNA testing system (8). On the basis of the individual genetic data thus obtained, and through the use of the current IrisPlex, HIrisPlex, und HIrisPlex-S models (https://hirisplex.erasmusmc.nl/), individual probability values (test results) for three categories of eye color, four categories of hair color, and five categories of skin color were calculated and are shown to the right of each phenotype photograph. The individual test results shown here are not to be confused with test accuracy values, which are listed in Table 1.