Under what circumstances can it be virtually certain that two fabrics share a common origin?

Two fabrics can be considered to have a common origin when their fibers can be fitted together at their torn edges. This direct physical evidence indicates that the fabrics were part of the same item before being torn, which strongly suggests they originated from the same source. Fitting the torn edges together allows a forensic examiner to determine not just a similarity in material but an exact match in the way the fabric was torn, thereby reinforcing the probability that both fabric pieces are from the same source.

In contrast, while matching colors could suggest a shared origin, it does not provide definitive proof, as two different fabrics can be dyed to the same color. Similarly, fabrics made from the same type of fiber do not guarantee they come from the same source, as many fabric manufacturers use similar materials for different products. Finally, being stored in the same location lacks enough specificity to indicate a shared origin, as multiple unrelated fabrics can be stored together without any direct connection between them.