Detection of Firearm Imprints on the Hands of Suspects: Effectiveness of PDT Reaction

Abstract

Pyridyldiphenyl triazine (PDT) and three of its analogues were compared as practical reagents for visualizing unseen impressions left on the hands of a person who has held a firearm. The parent compound, PDT, gave the best results using intensity and clarity as measuring criteria. The effectiveness of the PDT reaction was then studied on 147 volunteers who had held firearms in their hands. Identifiable impressions of the metallic parts of the weapons were developed on the hands of 103 volunteers (70%). Results with females were slightly higher than with males, however, the difference was possibly statistically insignificant, and needs further study. Ferroprint™ and Ferrotrace™,5 commercial preparations that are based on the PDT reaction, have become a part of the professional equipment of every crime scene technician in Israel.

Recent developments in methods of chemical analysis in investigations of firearm-related events

“…Spraying hands with water, or even washing them under the tap, after Ferroprint application, accelerates color development without blurring the marks. In a study [62] involving 147 volunteers, both male and female, it was found that marks of strong and medium intensity developed (immediately after contact) on over 70% of the volunteers without substantial differences between males and females. In this study, three analogs of PDT (one, IDT, producing dark gray impressions on the hand), were also examined on 15 volunteers.…”

“…A series of studies on the reagent 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT, Fig. 7) and its analogs for visualizing traces of iron on hands was recently conducted by Almog et al [57,58,59,60,61]. PDT reacts with ferrous ion to give a magenta complex.…”

“…From casework experience of using Ferroprint in Israel it seems that most of the benefit of using the test is in confirming suicides. It can also be useful in determining the murderer in homicide-suicide cases where the evidence at the scene of crime is impaired intentionally [61]. Although no comprehensive study has been performed on the safety of PDT, to date no health hazard has been encountered with PDT during more than ten years of use by the Israel Police [62].…”

Children and guns: The detection of recent contact with firearms on children's hands by the PDT reagent

“…The influence of several factors on the quality of iron-PDT marks, such as the gripping duration and the effect of washing the hands, has been reported earlier [19,20]. In a recent study two techniques which are based on better understanding of the physiological processes which take place on the skin, have been devised and tested for the enhancement of the sensitivity of this process: exposure to water vapors and accelerated sweating [28].…”

“…One forensic method that approaches the crucial question ''Who held the gun'', known as the Trace Metal Detection Test (TMDT), or the Ferroprint TM test, relies on the development of invisible iron marks on the hand of the suspect [18][19][20]. During the handling of a weapon, minute amounts of iron are transferred from the metallic parts of the weapon to the skin of the ''handler'' via perspiration [21].…”