Experience with the PCR-based HLA-DQ alpha DNA typing system in routine forensic casework.

The results of HLA-DQ alpha typing from 42 routine forensic cases using the polymerase chain reaction (PCR) were analyzed regarding the reliability, discrimination efficiency and informative value of this system in a given case. The cases included stain typing from a variety of different substates, i.e. blood and semen stains, mixed body fluids, single hairs, cigarette butts, material from fingernail scratches, as well as identification and paternity cases on postmortem and fixed tissue. A total of 125 individual stain and tissue samples were included. PCR amplification was achieved in 70% of these samples. In cases with mixed body fluids, e.g. sperm and vaginal cells from rape cases, DQ alpha typing was always carried out successfully. However, only approx. 42% of all samples that could be typed were relevant regarding the inclusion or exclusion of a suspect. This was mostly due to the limited number of alleles that can be typed at the HLA-DQ alpha locus or to the fact that the stain or hair samples did not originate from the perpetrator, but from the victim or from other persons not related to the crime.