Identification of menstrual blood by real time RT-PCR: technical improvements and the practical value of negative test results.

The identification of body fluids can be of crucial importance in forensic casework. Recently we have shown that the detection of cell- and tissue-specific mRNAs is a suitable technique to identify menstrual blood and semen. In this paper we present an improved method using real time-PCR and the menstrual blood marker MMP-7 which increases sensitivity and specificity. We furthermore demonstrate case examples described showing that the correct identification of samples as non-menstrual is likely to be in the focus of criminal investigations. Although negative test results may have a number of other reasons, the new technique provides quantitative results thus allowing a cut-off value for the control marker GAPDH to be defined, below which negative results for the menstrual blood marker MMP-7 allow the conclusion that the sample was indeed not menstrual blood. Using these data, it is possible to apply the molecular identification of menstrual blood to forensic casework considering both the limitations and the capabilities of the method.