法医学研究杂志

Evaluating the Dusting Methods of Latent Print Processing on Small Caliber Cartridges and Cartridge Cases

Abstract

Tassew Mekuria and Alexandra Lehosky

Fingerprint identification is one of the most important methods of solving crimes in the field of forensic science. Forensic scientists and researchers agree that finger prints are individual characteristics that can assist in identifying an individual person from a population. The most challenging duty of a crime scene investigator is to bring suitable finger prints from crime scene to the laboratory. Barriers between surface type, texture of surface, size, shape, contamination, and other multiple factors could be listed as limitations of developing suitable latent finger prints. Undischarged cartridges and discharged cartridge cases are more challenging items for latent finger print processing personnel. Because finger prints are composed of about 98% water, 2% fats (oils) and other components, any latent prints deposited on cartridges prior to being discharged are either burned off from the heat of the discharging, and/or stripped away during extraction as the fire arms goes through the cycle of fire. Human factors, environmental factors and surface area to volume ratio can also play a role in the deposition of latent prints on small sized cartridges and cartridge cases. In this research, we evaluated the dusting methods used for developing latent finger prints from small sized undischarged cartridges and discharged cartridge cases.

We conducted experiments on 143 cartridges and cartridges cases of different calibers and metal alloys in controlled environments by considering different factors. The results showed that no suitable latent finger prints were developed from cartridge cases. Only 5 suitable prints were developed from brass 45 auto undischarged cartridges. Baltimore Police crime laboratory’s call history for 5 past years showed that many thousands of cartridges and cartridge casings were collected from crime scene. However, the numbers of suitable latent fingerprints developed in the past 5 years are not significant. We surveyed Baltimore Police crime laboratory personnel who served as a mobile unit or crime scene science unit technicians, with 1 to 40 years of service experiences and 97% of the responses showed that suitable latent finger prints were not developed via dusting methods from cartridges and cartridge cases. We also extended our questionnaires to 5 randomly selected sister-state laboratories to share their experiences on development of latent finger prints using dusting methods. 2 state laboratories reported that, they do not practice this method on cartridges and cartridge cases at all. The other 2 states reported that they also found out the dusting method as a non-effective method and they are looking for some other method to replace dusting. The 5^th state reported that data was not available to share.