DNA analysis of abortion material assisted by histology screening

In cases of rape leading to fertilization, paternity testing can retrospectively identify the assailant. Abortion material commonly represents a mixture of maternal and fetal tissue and blood, which cannot be differentiated with the naked eye. Consequently, DNA typing of abortion material may be complicated, including band overlap if maternal tissue predominates. Therefore, histology screening of the abortion content for typical fetal tissue components, such as chorionic villi, followed by selected DNA typing of this sample is suggested. This combined approach is illustrated by a selected case demonstrating the reliability and concurrence of the histology and genetic results.

Criminal anticipation of DNA investigations resulting in mutilation of a corpse

A corpse of a female was found in her apartment in a state of advanced putrefaction. Both hands were amputated, the external genitals were excised and the body parts had been removed from the scene. The subsequent investigations proved that the body parts had been severed post mortem. The cause of death was determined to be manual strangulation. A 33-year-old man later confessed that he had strangled the victim 9 days prior to discovery of the body and that he had had sexual intercourse post mortem. According to the confession, the rational motive for the subsequent mutilation was to eliminate biological stains (e.g. semen inside the vagina, epithelial cells below the fingernails from scratching) suitable for forensic DNA analysis. This constitutes a new type of defensive mutilation intended to prevent the identification of the perpetrator. An increase in the occurrence would be detrimental to the elucidation rate of homicides: in a total of 171 homicides investigated at this institute, DNA analysis of biological stains gave reliable evidence in 45 cases.

Multiple entrance wounds from one bullet due to the use of a silencer

When a bullet strikes an interposed object before entering a body, the bullet may fragment, or particles from the interposed object may be accelerated. Such secondary missiles may cause multiple entrance wounds if a body is located in line with their flight path. In the unusual case reported here, a silencer acted as an interposed object. The bullet disintegrated completely after impact with the central part of the silencer baffles, which were misaligned. Some bullet fragments were retained inside the silencer, and some exited as a collection of missiles, comparable to shotgun pellets. From a distance of several meters, the fragments wounded the victim at seven different anatomic sites. Use of a silencer should be considered when bullet fragments are recovered from a scene or victim but no other appropriate interposed object is found.

Experimental bloodstains on fabric from contact and from droplets

The differentiation between contact bloodstains and stains produced by projected droplets on fabric can be crucial in crime scene reconstruction since suspects can explain bloodstains on their clothing by contact with the victim post mortem. Experimental smear and contact pressure stains on three different types of fabric were compared with stains produced by falling and projected droplets ("dynamic" stains) of equivalent size. The morphology of the small stains (0.1-10 microliters) was investigated with a macroscope. Characteristic for "dynamic" stains are symmetry and rhythmicity (secondary droplets) of the stain and a zonal drying pattern. Contact stains lack the characteristic features of "dynamic" stains and show a clear impregnation of the material resulting in a blood-soaked reverse side of cambric and cotton and in a paler overall colour. The mode of formation of microstains (blood volume 1 < microliter) on irregular surfaces (e.g. terry cloth) can be difficult to determine since the rough surface structure and the small blood volume reduce the characteristics of dynamic stains. In these cases, comparison with experimental stains on the same surface material is recommended.

Microsatellite polymorphisms reveal phylogenetic relationships in primates

We amplified, via PCR, DNA segments from intron 1 of the tyrosine hydroxylase gene (TH01) and intron 40 of the von Willebrand factor gene (VWA) in ten nonhuman primate genera. In humans both introns contain polymorphic microsatellites with tetrameric repeats. Compared to the allelic ranges in human populations relatively short repeat arrays could be detected for the nonhuman primates typed, presumably reflecting an ancient precursor state at both microsatellite loci. Furthermore, our results provide evidence for an association of the average number of repeats present in different primate genera and their divergence time from man. DNA sequencing of VWA orthologues revealed a relatively high variability in the arrangement of repeats in the 5'-repeat arrays, the generation of which could probably be explained by polar mutational events.

Use of single- and multi-locus and polymerase chain reaction systems for zygosity determination--clinical application in twins with clefts of the lip and palate

Precision of zygosity determination in twins can be improved by the use of modern methods of DNA analysis. The clinical application of 4 single- (SLS) and 2 multi-locus (MLS), and 6 PCR (polymerase chain reaction) systems for zygosity determination in 12 twin pairs with oral clefts was compared with regard to the quality and quantity of sample material required and the probability of error in monozygosity determination. PCR systems proved to be superior to SLS or MLS, as DNA sampling is much more convenient, while its level of accuracy still fulfils clinical requirements. For this reason, PCR systems should be considered a basic method in modern clinical twin research.