Revista de investigación forense

Bullet-Weapon Determination on Highly Deformed Bullets (HDB): A Digital Device and a Mathematical Formula Method

Abstract

John Z. Wang

During drive-by shooting, police barricade, or armed bank robbery incidents, bullets hitting from a right angle onto a hard surface (car metal, concrete, or brick walls) usually turn into highly deformed bullets (HDB) on the ground due to the heavy impact. From the perspective of forensic practice, these HDBs bear little information due to the fact that there is only one or two rifling’s (lands/grooves) usable on the HDBs for the firearm examination. While the number of rifling is one of the standards or criteria for a bullet-weapon determination, an HDB with only one or two visible lands or grooves renders it little evidential value for identification. With a quasi-experimental design and a purposive sampling, two pairs of highly deformed jacked bullets (9 mm and .30) and one pair of highly deformed lead bullet (.38) were selected for testing and calculating. Using a palm-sized digital device, the study proposes a new mathematical formula that allows calculating the number of rifling on HDBs fired from pistols or revolvers. This new approach is able to provide a real-time method of determining the number of rifling’s on the HDBs to improve crime scene investigations as well as later lab work for bullet-weapon identification.