Detection of recent holding of firearms: improving the sensitivity of the PDT test.

Despite the significant improvement of the PDT test for detecting recent contact with firearms, there are still many occasions in which the modified reagent (Ferrotrace™) shows insufficient sensitivity. Two techniques have been devised and tested for the enhancement of the sensitivity of this process: exposure to water vapors and accelerated sweating. Exposure of the hand to water vapors after spraying with the reagent significantly improved the quality of the colored impressions. The average increase was by 1 quality-grade (on an arbitrary scale of 4 grades). The technique is very simple and does not require any particular skill or equipment. Mechanistic aspects of the process are also discussed.