Empirical proof of physical match: Systematic research with tensile machine

In forensic literature a physical match is often regarded as conclusive evidence, but Daubert ruling may change this. Every layman can determine physical match, and yet the individuality of physical match was never proven scientifically.Usually, tearing conditions are irreproducible. The direction and tearing force, and the nature and thickness of the substrate may vary. These varying parameters influence the advancement of the tear.This study tests if a tear remains unique, even when the tearing process is conducted under measurable and reproducible conditions. Substrates with homogenous properties were chosen. A standardized tensile machine with set force and speed conducted the tearing.Each torn sample was composed of two rims of the tear. A portion was cut from one rim, and the experts tried to find the fitting place on the opposite rim in a “double blind” test.Results of the study show that even tearing under repetitive conditions yields a unique contour for each sample, for the chosen materials and for length greater than 1 cm. Thus, it is demonstrated that individuality of the process is due to the material's internal structure.