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Specific Heat Capacity Thermal Function of the Cyanoacrylate Fingerprint Development Process

NCJ Number
Date Published
93 pages
In attempting to understand and improve the polymerization process of cyanoacrylate (superglue) fuming in developing latent fingerprints on nonporous surfaces, this research focused on temperature and humidity variations of both the environment in which the fuming occurred as well as temperature variations on the evidence.
The study concluded that latent fingerprints on nonporous surfaces that are developed with cyanoacrylate fuming achieve a higher level of polymerization when the surface temperature of the evidence is lowered, although overdevelopment can occur if the substrate is too cold. The research confirmed the initial premise that the temperature of the substrate material during the fuming event, combined with the relative humidity is critical in obtaining the best possible fingerprint development. The research further confirmed that the specific heat capacity and thermal conductivity of the evidence substrate material guides the temperature parameters of the polymerization process involved with cyanoacrylate fuming. On identical materials with deposited latent fingerprints developed simultaneously but at different substrate temperatures, researchers found a substantial increase in polymerization that is easily observed visually and supported by measurable weight increases when the evidence is cooled to a temperature relative to the substrate's specific heat capacity. The weight variations shown in the data files support the visualization properties, which is the main concern of latent fingerprint examiners. Further research with other substrate materials such as plastics and various metal alloys that were not included in the current testing will be required to narrow the temperature range specific to those materials; according to the findings of the current research, the temperature curve will follow the thermal conductivity profiles of common materials. A more focused study of the precise amount of relative humidity may result in increased sensitivity, but the current research shows that a range of 46 percent to 72 percent relative humidity is safe and conducive to cyanoacrylate polymerization on latent fingerprints. Extensive table and figures, and 12 references

Date Published: January 1, 2009