Pretreatment strategies for the improved cyanoacrylate development of dry latent fingerprints on nonporous surfaces

Cyanoacrylate fuming is a popular technique commonly used by evidence examiners for the development of latent fingermarks on nonporous surfaces. The process involves the preferential formation of hard, white polycyanoacrylate along the ridgelines of the fingerprint as opposed to the substrate background. This preferential deposition results in contrast between the fingerprint and substrate. This contrast may be further enhanced through the use of staining techniques such as rhodamine 6G. Because the cyanoacrylate mechanism is believed to be initiated by fingerprint constituents and catalyzed by moisture, it follows that fingerprints subjected to harsh conditions (e.g., heat, low humidity, or UV light) often produce poorly developed results. This study aimed to further investigate and validate the use of 10% w/v methylamine as a pretreatment strategy to overcome the limitations associated with the cyanoacrylate development of dry fingerprints and to compare the results with those obtained using previously proposed pretreatment solutions. The effectiveness of this treatment was demonstrated on samples similar to those encountered in casework, and scanning electron microscopy (SEM) of the treated fingerprints confirmed the rejuvenation of the dry latent deposits through a qualitative assessment of the polymer morphology.