[Sex identification of forensic biological materials]

The progress of sex identification methods for forensic biological materials such as dried bloodstains and others is reviewed on the basis of results obtained in our laboratory. Barr and Bertram (1949) discovered sexual dimorphism of mammalian interphase nuclei based on the presence of sex chromatin in the female and its absence in the male and also recognized a similar sex difference in human cells. Davidson and Smith (1954) first demonstrated sexual dimorphism in the polymorphonuclear leucocytes in the peripheral blood in man based on the presence of drumstick in the female and its absence in the male. Dixon and Torr (1956) first utilized the sex chromatin in the female nucleus to determine the sex from forensic materials. Matsumoto (1959, 1960) described a method to identify the sex from dried bloodstains by detecting drumstick. In general, however, the use of drumstick for the sex determination from dried bloodstains is very difficult because of a low frequency of drumstick itself and deformities of leucocyte nuclei in the stains by drying. Late in 1971, we introduced a method for detecting Y chromatin in the interphase nuclei of human male by fluorescent microscopy as a new tool for decisive male sex determination from forensic materials. This method was accepted as the reliable means to identify sex in forensic medicine. Since 1980, we have studied to identify sex from bloodstains by the ratio of sex hormones, testosterone and progesterone, determined by radioimmunoassay (RIA). We also examined the method of Witt and Erickson (1989) to detect Y and X chromosome specific DNA sequences using the polymerase chain reaction (PCR), and we improved this technique to exhibit its ability to identify sex from forensic materials. Our improved PCR method is thought to have a broad applicability to forensic practice because of its simplicity, sensitivity and reliability.