Scientific Evidence in Criminal Cases

Abstract

Judicial tribunals usually exercise considerable caution regarding the admissibility into evidence of expert testimony concerning some new phase of our ever increasing wealth of scientific knowledge. In certain instances this attitude has led courts of justice to reach apparently absurd results. The scientist occasionally reads with scorn the judicial denunciation of, or the refusal to consider, the application of a scientific principle or instrumentality. Yet the conscientious scientific investigator himself exhibits the same degree of caution, if not more, whenever there appears the announcement of some alleged discovery or invention.

Topography measurements for determining the decay factors in surface replication

“…When the bullets and casings are fired or ejected from a gun, both the macro and micro topography features on the gun parts are picked up by the bullets and casings and form the characteristic features on their surface. The macro topography includes the number, shape, size, direction and angle of the twist of the gun barrel, which contacts with the bullet during firing; and the geometrical size, form and waviness of the firing pin, breech face and ejector which contact with the casing [8]. The macro topography features represent the common characteristics of a group of guns manufactured from the same design, manufacturer and tooling process.…”

“…The macro topography features represent the common characteristics of a group of guns manufactured from the same design, manufacturer and tooling process. When the macro topography of the gun parts is striated or impressed on the surface of the bullets or casings, their common characteristics form the 'Class Characteristics' (as called in forensic science [8]) of bullets or casings. The 'Class Characteristics' are similar between bullets or between casings fired from guns manufactured from the same production line.…”

“…The 'Class Characteristics' are similar between bullets or between casings fired from guns manufactured from the same production line. In forensic science, 'Class Characteristics' are used for the identification of the type and manufacturer of a weapon [8]. On the other hand, the micro topography or surface roughness on the gun parts represents, in addition to stochastic differences, the unique characteristics of the gun.…”

“…The micro topographies are unique for different guns even manufactured from the same production line one after another. When the micro topography of the gun parts is striated or impressed on the surface of the bullets or casings, its unique characteristics formed the 'Individual Characteristics' [8], or ballistics signatures. In forensic science, 'Individual Characteristics' are used for the identification of an individual firearm, and to connect the fired bullets or casings to a firearm and criminal acts [8].…”