Murder by the Book: William Overson
On August 13, four months after the homicide, Deputy District Attorney Jim Koerber filed murder charges against Derieux and Bruce. (Earls, whom Koerber hoped to flip against his co-conspirators, was not publicly identified.) Although authorities were certain they had the killers, the case was far from locked up.
Detectives hoped that ballistics tests could confirm that the gun remnants found under Fritz Bruce's bed were those of the weapon used to kill Overson.
Rifle barrels are grooved to increase a fired projectile's distance and accuracy. This rifling creates distinct scratches and indentations on the fired slug, similar to a fingerprint. For more than a century, ballistics experts have been able to match slugs fired from the same weapon, and this form of evidence has been featured in courtroom testimony in countless criminal prosecutions. But the barrel of the .223 was not intact, which made testing it much more difficult.
Mary Jane Flowers, a San Diego police forensic criminologist, made a series of test fires through the lower portion of the barrel, but the results were inconclusive. She asked Timothy LaFrance, a renowned gunsmith who often works as a police consultant in difficult ballistics cases, to reassemble the barrel. LaFrance agreed to take on the risky work. Gun barrels are not meant to be cut then put back together. Every shot from a firearm is a controlled explosion, with expanding gas pushing a projectile down the barrel at great speeds. Any flaw in the barrel or the firing chamber can cause a potentially deadly fragmention of the gun metal.
LaFrance's first attempt to reforge the Ruger's barrel into one piece failed in its first test fire. He tried again and managed to stabilize the barrel long enough to make six successful test fires, pulling the trigger from a remote location, in case the gun blew apart. When LaFrance and Flowers compared the rifling marks on the test slugs to those from the murder, they concluded that without question the Ruger Mini-14 found under Bruce's bed had been used to kill William Overson.