Examples for use of the STR systems in stain assessment with special reference to Y chromosome systems

The authors describe 3 cases where Y-chromosomal systems were used for typing the biological traces. In the first case, a murder, for the major amount of cell material found on a dish towel (and analysed two years after the crime) female persons were excluded for the system amelogenin and Y-chromosomal systems. A brother of the victim could not be excluded for autosomal STR-systems. Upon confrontation with the results of the DNA-analysis (among other things), this brother confessed the murder of his sister some days later. He was found guilty by the court. In the second case described, a rape of two girls, many traces were analysed parallely with Y-chromosomal and autosomal PCR-systems. The objects where male DNA matching the suspect were found (a paper tissue, a sweat shirt and the knickers of the girls), also showed small amounts of alleles matching with the suspect for autosomal systems, while the major part in these systems was from the girls. The suspect was sentenced to many years imprisonment. In the third case, a possible rape of a young woman, a stained microscope slide of a vaginal swab had to be examined. Microscopically a few sperm heads could be seen in a surplus of leucocytes. The male proportion could be analysed only in the Y-chromosomal systems, not in the autosomal ones. For the frequency calculation of the Y-chromosomal allele combination the haplotype data bank of the Institute for Legal Medicine of the Humboldt university in Berlin was indispensable.