From the early 1990s, automated identification systems for the
comparison of firearms evidence have been developed and used
with considerable success. However, the automated systems are
still in a stage of being used as preliminary search tools in an
investigation. They rank the bullets stored in the database in light
of a similarity metric with respect to a subject bullet. A universally
derived and statistically valid objective criterion has not yet been
developed to enable automated systems to partition matching and
non-matching bullets. The final decision whether two bullets were
fired from the same barrel is still made by examiners using manual
microscopic comparisons, and the ultimate determination of
identity is therefore subjective.