Alva Review-Courier -

CHICAGO (AP) — When Illinois jurors convicted Patrick Pursley of murder, they relied on an expert's assurance that the scratches and dents on bullets and shell casings from the crime scene proved they could only have come from Pursley's gun.

More than two decades later, technological advances have eroded confidence in ballistic experts, and the analyst who testified against Pursley is no longer so sure of his findings. Now Pursley is awaiting a new trial, and the case could become the first in which a database used to help put countless criminals behind bars sets someone free. The issue could...