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.     

Population data of nine Y-chromosomal STR loci in northern Poland

Allele and haplotype frequencies of nine Y-chromosome STR loci were determined from a sample of 508 unrelated males from north Poland. Three samples containing insertion polymorphism DYS19 (duplication) and DYS385I/II (triplications) were observed.     

Detection of Contact Traces of Powdery Substances

The current practice in securing the contact traces of chemical substances taken from clothes belonging to a person suspected of manual handling explosives is focused on pockets and cuffs. The outerwear worn by people who had contact with fluorescent powders that simulate explosives and drugs was the subject of this study. Clothes were first exposed to the test substance for a period of time and then analyzed by fluorescence methods to determine the location of the highest quantity of traces. The results obtained from the study confirm that the areas with the highest concentration of powdery traces are different from those suggested by current forensic practice. They appear to be promising for a more efficient identification of the suspects involved in illegal manufacturing of drugs of abuse or explosives. Moreover, they may be helpful for developing the methodology for handling the evidence material in the forensic clothing examination process.     

DNAc: A clustering method for identifying kinship relations between DNA profiles using a novel similarity measure

After decades of refinement, DNA testing methods have become essential tools in forensic sciences. They are essentially based on likelihood ratio test principle, which is utilized specifically, by using as prior knowledge the allele frequencies in the population, to confirm or refute a given kinship hypothesis made on two genotypes. This makes these methods ill suited when allele frequencies or kinship hypotheses are unavailable. In this paper, we introduce DNAc, a new clustering methodology for DNA testing based on a new similarity measure that allows an accurate retrieval of the degree of relatedness among two or more genotypes, without relying on kinship hypotheses or allele frequencies in the population. We used DNAc in analyzing microsatellite DNA sequences distributed among 12 genotypes from normal individuals from two distinct families. The results show that DNAc accurately determines kinship among genotypes and further gathers them in the appropriate kinship groups.     

The UNHCR's Guidelines on Human Trafficking

In April 2006 the UNHCR published Guidelines on the applicationof the Refugees Convention to people who have been trafficked.While there is little doubt that trafficked people are subjectedto serious violations of their basic rights and interests, theapplicability of the Convention is problematic because theydo not fit easily into any of the categories recognised by theConvention as giving rise to an entitlement to refugee status.The Guidelines adopt the definition of trafficking containedin the Palermo Protocol to the UN Convention on TransnationalOrganised Crime 2000. The various elements of the refugee definitionare then analysed for their relevance to trafficking. The Guidelinesshow that the Refugees Convention may be applicable, but inlimited cases, particularly through the possibility of victimsof trafficking being members of a particular social group.     

Validation of cytochrome b sequence analysis as a method of species identification

One of the stages of dealing with biological material submitted to forensic laboratories is species identification. The aim of the present work was to validate and assess the possibility of applying sequence analysis of the region coding cytochrome b as a method of species identification in the field of forensic science. DNA originating from individuals from major phyla of vertebrates was isolated by the organic method from various specimens. Extracted DNA was subjected to PCR and direct cycle sequencing using a universal pair of primers. The validation process, performed according to TWGDAM recommendations, revealed that the technique is a very sensitive and reliable method of species identification allowing analysis of tiny amounts of material and also degraded material, and can be useful in the field of forensic genetics. The case example presented here, concerning the determination of species origin of biological evidence collected from fatal road accident, confirms that analysis can be carried out even when there is no reference sample, and the sequences obtained can be assessed through analysis of their similarity to sequences for cytochrome b present in DNA databases.