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.     

Homicide by blunt force in 2 Scandinavian capitals

In the Oslo and Copenhagen areas, 77 instances of blunt force homicides were committed from 1985-1994, accounting for 18% of all homicides in that 10-year period. Fifty-four (70%) of the victims were male, often killed by an acquaintance during a fight. Almost 70% of the female victims were killed in their own home, whereas that was the case for only 30% of the male victims. The majority of the victims (of both sexes) had been hit in more than 1 region of the body. A female offender was encountered in 4 instances; none of their victims were children. Of the 3 children in the blunt force victim group, 2 were battered children. Many of the victims with a blood alcohol level of 0 turned out to have lived for some time after the injury.     

STR genotyping and mtDNA sequencing of latent fingerprint on paper

A systematic study was conducted to investigate whether DNA can be successfully extracted from latent fingerprints deposited on ordinary paper and analysed using short tandem repeat profiling and mitochondrial DNA sequencing. In order to evaluate the performance of latent fingerprint analysis in a criminal case, experiments with varying conditions were carried out to improve our understanding of low copy number (LCN) DNA typing. After optimising the extraction methods to achieve increased sensitivity, the examination of touched paper can routinely yield the STR profile of the individual who has touched it. A fingerprint can therefore be considered as a potential source of DNA for genetic identification. Nevertheless, the findings of our "after enhancement experiment" (using chemically or physically pre-treated fingerprints), and our "mixture experiment" (using fingerprints from three to four people on the same sheet of paper) help to define the limitations of the low copy number PCR technique in forensic casework.     

Determination of lysergic acid diethylamide in body fluids by high-performance liquid chromatography and fluorescence detection--a more sensitive method suitable for routine use

A new method for determination of lysergic acid diethylamide (LSD) in body fluids by high-performance liquid chromatography and fluorescence detection was developed based on previously published methods. The new method is suitable for confirmation of samples tested positive by immunoassay, avoiding loss of LSD by absorption to surfaces. The reduced loss of LSD results in improved sensitivity. This is achieved by adding ethylene glycol to the samples, which cover glass surfaces. This principle can similarly be used to improve analysis of other drugs. Body fluids for analysis included urine and whole blood. An internal standard was applied for quantification of LSD. The new method offers satisfying precision data and has a detection limit of less than 0.05 ng/nL.     

Neck extension as a cause of SIDS

The intradural sagittal diameter at the second cervical vertebra (SD/C2) of 62 SIDS cases was measured myelographically. This SD/C2 proved to be dependent on body size, body weight, and age. A clear, age-dependent difference is to be found in the primarily narrow spinal canal. This parameter (SD/C2), which is more precisely defined in adults on the basis of clinical, radiological, and autopsical findings is assumed to have the value of 0.5 cm in the first 2 months, 0.6 cm in the third month, and 0.65 cm in the fourth month. The resulting potential danger to infants is dependent upon their position. The SD/C2, was significantly decreased in extension as compared to a neutral posture. With consideration of the primarily narrow spinal canal in the infant, there is, according to our measurements, a potential hazard for the infant in any further, significant shortening of the SD/C2. This is independent of the width of the spinal canal under maximal extension. We found individual cases in which the SD/C2 was decreased by almost 50% from the normal value in neutral position. No correlation was found between the primary width of the spinal canal and the degree of luminal reduction upon extension.