Typing of human red cell and serum mixtures in three electrophoretic systems.

The isoenzymes erythrocyte acid phosphatase and phosphoglucomutase were typed in mixed red cell samples which had been derived from two individuals; the protein group specific component was typed in mixed serum samples. Typing was performed by isoelectric focusing on ultrathin polyacrylamide gels. Depending upon the mixture, from 2 to 20% (but typically 5-10%) by volume of a second blood or serum needed to be present in a mixture before it could be detected. In the majority of cases when there was significant mixing, samples were readily identified as a mixture when the results consisted of unusual band patterns or unusual band intensities. There would be a few instances when blood or serum could not be identified as a mixture when masking effects occurred or when the mixture produced a combined, apparently normal, pattern.     

Quantifiler observations of relevance to forensic casework

The Quantifiler (QF) kit is regularly used by forensic scientists for DNA quantitation. We performed in-house validation studies which revealed some interesting observations. The QF standard displayed a two-fold difference between two different lot numbers which suggests that every standard should be tested prior to use. The Promega K562 DNA standard works well with the QF kit. c. 41% of samples that inhibited the internal PCR control (IPC) system within the QF kit still produced good Profiler Plus reactions. QIAquick was effective at removing inhibitors. The presence of dyes within casework samples were observed not to inhibit QF amplifications. Template DNA greater than 100 ng/muL appeared to inhibit the IPC. Close to identical concentration results were obtained when alternative analysis settings were used. These validation findings will assist DNA processes involved in forensic casework.     

Alleged sexual violation of a human female by a Rottweiler dog.

An unusual case involving the alleged sexual violation of a woman by three men and a Rottweiler dog is described. Forensic examination proved difficult and showed little of evidentiary value but did reveal the presence of dog hairs at the scene, and semen from one of the men on the victim's panties. All attempts to locate and identify dog semen were unsuccessful. It was not clear whether dog semen could not be located using available techniques for semen identification, or whether dog semen was, in fact, not present at all.