Measurement of Scars Using Structured-Light 3D Scanning in Forensic Practice

Objective To validate the accuracy and reliability of structured-light three-dimensional （SL-3D） scanning in measuring the length and area of the regular and irregular scars on body surface and discuss its value in forensic practice. Methods The lengths of 30 cases of simulated linear scars and 50 cases of linear scars after injury were measured using soft ruler, vernier caliper + thin line method, and SL-3D scanning. The areas of 35 cases of simulated patchy scars and 15 cases of patchy scars after injury were measured using length × width, film tracing with coordinate paper method, pixel method, and SL-3D scanning, and then statistically analyzed. Results The differences between the length of the simulated linear scars measured by SL-3D scanning and standard length had no statistical significance. When simulated patchy scars and patchy scars after injury were measured with high surface curvature and large irregular areas, the differences between the results of SL-3D scanning measurement and the standard area had no statistical significance. When the length of 50 cases of linear scars after injury were measured using SL-3D scanning, the correlation coefficient between the measurement results of two different investigators was 0.998, and the correlation coefficient between the two measurement results by the same investigator was 1.000. The correlation coefficient between the results of SL-3D scanning and that of vernier caliper + thin line method was 0.996. Conclusion The three-dimensional information of the scars on the body surface can be acquired using SL-3D scanning. The measurement of the length and area of the scars is not influenced by the location of scars, curvature of surface, and human factors. The measurement results are accurate, reliable and has unique advantages.