Comparison of three bullet recovery systems.

Comparing the marks left on questioned bullets to those left on reference bullets is the main aim of a firearm identification expertise. Thus, producing reference bullets with a questioned firearm is an essential step. Different kinds of system have been developed to safely recover bullets fired from questioned firearms. However, the performance of each system and its impact on traces left on the bullets have not been addressed. Three bullet recovery systems - a horizontal water tank, a cotton tube and a recently designed fleece - were used to fire seven types of ammunition of various type, shape and casing. The bullets were then described and images of their surface were acquired with an automatic system to study the impact of each system on the bullets. The water tank is the more efficient system in terms of quality of the marks. However, it cannot be used to fire every type of ammunition. Some of them, such those used by law enforcement, tend to be damaged with this system. A way to mitigate the problem is to use the cotton or the fleece-based systems, the latter being more universal. It requires a cleaning step to remove all the fibres from the surface of the bullet, but the marks left by the weapon are still of interest.