This paper presents a study of the intra-individual variation of pubic hairs. Seventy pubic hairs were pulled from seven sites around the outer genital area of each of five Japanese males; sixty were obtained from six sites on each of four Japanese females, and fifty from six sites on one additional Japanese female. These hairs were examined with respect to twenty-two morphological characteristics. These morphological data were studied in relation to each site and analyzed by the statistical method of cluster analysis.
It appeared that a pubic hair's length, luster, diameter, medullary index, disease and scale damage bore some relation to the site from which it was obtained. Dendrograms produced through the cluster analysis showed a hierarchy of similarities among all pairs of pubic hairs. Similar hairs were placed together into several large or small groups within the same person. Some groups contained pubic hairs from many sites, whereas others were almost exclusively from only one site. This means that some sites have different characteristics from other sites. Pubic hairs obtained from the penis area, scrotum and labium majus area showed greater dissimilarity than other sites within the same person.
Therefore, in forensic hair comparison, known pubic hair samples should be obtained from many different sites. For males, at least thirty-five pubic hairs should be collected from seven sites (center, left and right abdomen; upper, left and right area surrounding the penis; and scrotum). For females, at least thirty pubic hairs should be collected from six sites (center, left and right abdomen; mons pubis; left and right labium majus).
