Reproducibility of Artificial Cut on Heel Area of Rubber Outsole

Randomly acquired characteristics (RAC) are seldom used for exclusion in footwear examinations because they can disappear owing to wear. To help examiners explain discrepancies in RAC, this study investigated the reproducibility of cuts. One cut was made on the heel area of each shoe outsole and then measured. Changes in cuts were statistically evaluated, correlations between their variations and the weight/height of the subject were assessed, and the Support Vector Machine was used for the first time to study their discrimination probability. Most cuts became larger at first and then became smaller. The solidities of most cuts increased after 21 days, and the variation in the cut and the subject's weight/height were negatively correlated. Although the discrimination probability declined as the cut aged, 77% of the same-source and 96.88% of the different-source cuts could be identified correctly after 6 months, indicating that cuts on the heel area are relatively reliable.