Forensic age diagnostics of living people undergoing criminal proceedings

In the German-speaking area, recent years have seen a rapid growth of the need for forensic age estimations. Such need arises, for example, if no verified information on the age of a person suspected of a criminal offence is available; the issue at question in terms of criminal law is whether the person concerned has reached the age of criminal responsibility and whether general criminal law in force for adults is to be applied. The relevant age tresholds in criminal proceedings are 14, 18 and 21 years of age. According to recommendations of the Study Group on Forensic Age Diagnostics, a forensic age estimate should consist of a physical examination, an X-ray of the hand, and a dental examination which records dentition status and evaluates an orthopantomogram. In addition, a radiological or CT examination of the clavicles is recommended to establish whether a person has attained 21 years of age. The present article addresses the influence of ethnic origin on the examined developmental systems.     

STR analysis of artificially degraded DNA-results of a collaborative European exercise

Degradation of human DNA extracted from forensic stains is, in most cases, the result of a natural process due to the exposure of the stain samples to the environment. Experiences with degraded DNA from casework samples show that every sample may exhibit different properties in this respect, and that it is difficult to systematically assess the performance of routinely used typing systems for the analysis of degraded DNA samples. Using a batch of artificially degraded DNA with an average fragment size of approx. 200 bp a collaborative exercise was carried out among 38 forensic laboratories from 17 European countries. The results were assessed according to correct allele detection, peak height and balance as well as the occurrence of artefacts. A number of common problems were identified based on these results such as strong peak imbalance in heterozygous genotypes for the larger short tandem repeat (STR) fragments after increased PCR cycle numbers, artefact signals and allelic drop-out. Based on the observations, strategies are discussed to overcome these problems. The strategies include careful balancing of the amount of template DNA and the PCR cycle numbers, the reaction volume and the amount of Taq polymerase. Furthermore, a careful evaluation of the results of the fragment analysis and of automated allele calling is necessary to identify the correct alleles and avoid artefacts.