Page 14 - Shot In The Dark Bullet Striations

comparison objects are lined up to find similarities. cartridge case, and a firearm are all present.
If similarities are not found between the bullets, When the bullet is collected, it is rarely found in
they cannot be associated with a common gun. perfect shape without deformation, however, it is
Bullets are typically examined under a reflective relatively easy to assess the caliber of the bullet,
light with a magnification between 5x and 100x. thus, narrowing down the type of gun used in the
crime. Once the caliber is determined, the goal of
Comparison microscopes are still today used in the examiner is to determine if the bullet from the
ballistic imaging comparisons, however many crime scene was fired from the gun in question
improvements to their accuracy and efficiency have (usually the gun associated with the criminal or
been made since that time. Modern comparison defendant). The grooves and lands imprinted
microscopes have video capabilities, digital imaging, on the bullet must be analyzed by a computer-
and fiber optic illumination allowing photos to be taken imaging program or a trained human examiner. If
for future reference and courtroom presentation while a computer-imaging program analyzes the bullet
the bullets are in the microscope. Visualization tools and finds a match, the evidence will still require
have also been developed that mimic the operation of confirmation by the expert examiner. When this
the comparison microscope. These programs often evidence is presented in court, a computer match
give the viewer the option of a 2D or 3D view of the cannot stand on its own; a ballistic examiner is
surfaces and even allow the examiner to examine required to confirm the match in order to allow
striae in comparison with one another by overlapping the ballistic imaging and computer match to be
the two. While many refinements have been made to considered evidence, as the expert examiner may
the original model, remarkably, it remains the same be called upon to testify in court.
basic concept Goddard developed nearly a century
ago. With this important technological advancement, When a gun is found that could possibly be the
ballistic imaging became an important aspect of the origin of a fired bullet, it must be able to produce
forensic sciences. a consistent pattern of grooves and lands
on subsequent bullets fired into a controlled
When examiners are looking at the evidence at environment. This controlled environment is
a crime scene, in the best case scenario a bullet, usually a tank of water designed to slow a bullet’s

14 THE MYSTERY OF LYLE AND LOUISE