Preliminary study of hair form of Japanese head hairs using image analysis

The use of average curvature measurements for the forensic comparison of curly hairs has been reported, but a method, in which various types of hair form are quantitatively examined and objectively interpreted for hair comparison, has not been reported to date. In the present study, numerical data on hair form from Japanese subjects were obtained by image analysis and a morphological comparison of these head hairs was investigated. Head hairs obtained from eight Japanese males were measured for length (L), distance (D) and area (A) using a Kontron Imaging System KS400. From the three measurements mentioned above, three indexes, L/D, A/D and 2(A/L), were examined. The inter-individual variations for each value were investigated by a t-test and the availability of six values for the forensic comparison of hair form was evaluated by a stepwise linear discrimination analysis. Six values obtained from hair form by an image analysis showed large intra-individual variations. However, these six values were found to be useful for discriminating between two individuals, since the six values showed larger inter-individual variations than intra-individual variations. Discrimination on each comparison using a stepwise linear discrimination analysis was performed for some of the values and the results indicated conspicuous inter-individual variations between the two individuals. On 11 of 28 comparisons, 30 hairs from one individual could be completely distinguished from hairs of another individual, when a two-way comparison was employed. These results confirm that hair form could be quite useful in the forensic comparison of hair morphology, and suggest that numerical data obtained from hair form by image analysis are very important values for constructing a screening procedure for evidential hairs. The use of an objective measure of hair form will be especially useful for Japanese head hairs since they are generally thought to show very limited variation in morphological features.