Content area
Full Text
Abstract: The Liqui-Nox/black powder process was examined as a means of developing fingerprints on the sticky side of duct tape.
Introduction
Duct tape is one of the most common adhesive tape exhibits. It is frequently used as a wrapping for drug packages, a reinforcement for the stocks of sawed-off firearms or as a means to bind a victim. Currently the gentian violet process is routinely used to develop fingerprints on the sticky side of duct tape.
The nature of the sticky side of duct tape was examined in close detail and the development of fingerprint impressions on this surface using the Liqui-Nox/black powder process was explored.
Materials
Distilled water
Liqui-Nox glassware cleaner
Lightning black fingerprint powder
Duct tape
Method
Fingerprint impressions were placed under various conditions on the sticky side of lengths of duct tape. Different pressures of application were compared. Impressions made by fingers cleansed of sweat and oil were compared to the impressions made by fingers rubbed against oily skin areas contaminated with sebaceous materials. Single verses multiple touches were also examined. Resulting impressions were observed under 8X to 25X magnification.
The sticky side of tape was then processed with Liqui-Nox/black powder and resultant print development documented. Observations
1. The substrate.
The surface of the tape was examined under 8X and 16X magnification. Details of the adhesive emulsion are clearly visible on the inner surface of the tape. The surface appeared to be generally smooth and viscous. The lines of the reinforcing thread running through the frontal surface of the tape itself could be observed as high and low areas in the adhesive. There were deep indentations and bubbles in the surface of the adhesive created by the manufacturing process of the tape. These were clearly visible under 8X magnification. Objects placed in contact with the surface and then removed left clear disturbances in the surface of the adhesive.
The point of a pin when placed against the surface then withdrawn was observed to cause the adhesive to stretch upwards into a pointed feature. Over time the feature slowly subsided. However, evidence of the pin touch remained as a visible mark on the surface. A coin rolled across the surface on its edge was observed to leave a definite indentation of...