Traceability for ballistics signature measurements in forensic science

The National Institute of Standards and Technology (NIST) in collaboration with the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) has developed the Standard Reference Material (SRM) 2460 Bullets and 2461 Casings. NIST has also developed a 2D and 3D Topography Measurement and Correlation System for ballistics signature measurements. This system includes stylus instruments and a confocal microscope for 2D and 3D topography measurements, and a 2D and 3D topography correlation program developed by NIST. NIST and ATF are proposing to establish a National Ballistics Measurement Traceability and Quality System using these materials. In this paper, basic concepts and specific requirements for establishing ballistics measurement traceability are introduced; three key issues are discussed that include: (1) establishing a reference standard; (2) establishing an unbroken chain of calibrations; and (3) evaluating measurement uncertainty for both the geometrical topography measurements and the optical image correlations of the ballistics signatures.