Specific Heat Capacity Thermal Function of the Cyanoacrylate Fingerprint Development Process, 2012
Charles A. Steele, Mason A. Hines, Lara Rutherford
See also the instructional videos on "Latent Fingerprints"
Abstract
Multiple methods were explored to increase the resolution of fingermarks obtained through cyanoacrylate (CA) fuming, or improve the ease of resolving fingermarks.
The first method explored was the development of sublimation based co- polymerized coloring. This research stream is an expansion of the work which produced CN-Yellow with an attempt to stretch the excitation range of the fluorescent effect to 530 nm so that it can be used with existing lasers. Many different colorants were evaluated for appropriate fluorescent responsiveness. Once appropriate colorants were identified, they were co-fumed with CN-Yellow in a closed chamber and evaluated with an ALS for detection at 530nm. Colored CA Fingermarks, detectable with a 530nm laser, were successfully produced.
The second method explored was the modification of evidence temperature. Samples of multiple materials were cooled 6°F-20°F below ambient and were CA fumed side by side with fingermarks which had not been cooled. The resulting fingermarks were weighed, tested for opacity and color uptake via dye staining. Our research as shown improvements in visibility: due to increase in opacity and color uptake, of CA fingermarks when the evidence is cooled 6°F-20°F.
The third method explored was the use infrared detection. Fingermark samples were prepared on Plexiglas and aged for two weeks to allow them to fade. The samples were then examined with infrared cameras at ambient temperature and cooled to force condensation and improve infrared visibility. While methods did yield fingermarks, no prints were resolved which would not have been detectable by more economical visible light means.
The fourth aspect of the research was to find a way to disperse nano-particles onto CA prints. Nano-particles can be applied in a variety of ways ranging from spraying liquid dispersions to creating dust clouds. However, when the particles are produced on the fingermark itself, it is possible to lock the color into the CA matrix with subsequent fuming. Carbon black nano-particles were therefore produced by burning oil and directing the vapor stream onto the print.
The final aspect of the research was to develop a commercially viable temperature and humidity controlled chamber to chill the evidence and allow for standard fuming. A unit was developed and can be purchased through Sirchie Corporation.