Reliability study of the Chinese method for bare footprint linear measurement

In many countries, bare footprints collected from crime scenes can be used as evidence for forensic identification, which involves the linear measurement of quantitative characteristics. Compared with several other methods of footprint measurement, the Reel method has been proven to be reliable and has been used in many countries. The Chinese method for bare footprint measurement is the official method issued by Ministry of Public Security of China, but its reliability has not been tested. This study focuses on the reliability test of the Chinese method for bare footprint measurement, which can serve as a reference for the verification in the process of footprint identification. Sixty-four volunteers were randomly selected to make dust and inked footprints, and five metrics of each footprint were measured and re-measured by three raters to test the reliability. These metrics consisted of four main ones from the Chinese method, with one from the Reel method for comparison. Based on intraclass correlation coefficients, the standard error of measurement and 95% Bland-Altman limits of agreement, test-retest reliability, and rater reliability within and among three raters were analysed. The Chinese method finally demonstrated a high degree of reliability. Although the Reel method achieved a marginally higher reliability score, its advantage was slight. Furthermore, the Chinese method for bare footprint measurement is not only reliable but also simple to operate, making it a viable supplement to the Reel method in contexts outside of China. In the process of footprint identification in China, when footprints are re-measured or measured by different appraisers for verification, the reliability values given in this paper could be used as a reference.