Poetsch L.^*, Schneider P.M.^*, Lummer J.^*, Skopp G.^**

^* Institut fur Rechtsmedizin der Johannes Gutenberg Universitat, Am Pulvertutm 3, 55131 Mainz, Germany
^** Institut fur Rechtsmedizin der Ruprecht-Karls-Universitat, Voßstr.2, 69115 Heidelberg, Germany

The increasing interest in alternative biological matrices for toxicological information on drug use is due to improved analytical instrumentation, the possibility of an historical record of drug use provided by these specimens and the advantage of non invasive sampling. However, there might be a higher risk for these samples than for blood or urine, that the chain of custody is disbelieved and the identity is denied.
Hair fibers, hair roots, fingernail clippings, transdermal collection devices, skin swabs, saliva, oral swabs, as well as the corresponding blood samples of 10 persons were under investigation. After DNA extraction PCR (polymerase chain reaction) was performed. STR's ( short tandem repeat systems) were separated by electrophoresis, for HLA-DQa typing a commercial test kit (Perkin Elmer, Cetus Emeryville, USA) was used. Identity could be always established for hair roots, oral swabs and saliva. PCR failed in some cases for sweat patches, skin swabs and fingernail clippings. Identity could not be established in cut hair samples.
This result stresses the necessity and underlines the importance to ask for a few plucked hair fibers in addition to the cut hair sample in forensic hair analysis.