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SU Forensic Experts Demonstrate Impact of Surface Absorbency on Fingerprint Distortion
Forensic fingerprint analysis involves more than lifting a clear print off a surface, as there is often distortion caused by the movement and pressure of the finger when the print was made. In the forensics field, this is referred to as latent print distortion.
In a recent paper published in the Journal of Forensic Science, two adjunct faculty members in the College of Arts and Sciences’ Forensic and National Security Sciences Institute, demonstrate the differences in latent print distortion on absorbent surfaces—such as paper—and non-absorbent surfaces—such as ceramic tile.
“In the process of analyzing a print for identification, you have to take into account various factors of distortion. Some can be very complex, so it helps to have a good grasp of different distortion factors,” says co-author David Tate, a certified latent print examiner.
Distortion mechanics delve into the minutiae of latent print analysis and are aimed at having a greater impact on the examiner’s accuracy when marking features within the latent print, and ultimately, in determining its value and correspondence (or lack thereof) to a known subject’s impression.
Tate and co-authors Jesse Eller and Elizabeth Anderson G’15, conducted a study comparing lateral movement of fingerprints—essentially swiping a finger along a surface—on copy paper and on ceramic tile. Their results showed that indeed, the porosity of a surface impacts print distortion. “The distortion of a print will have a different appearance based on the surface,” says Tate.
In particular, the clarity of the impression at the beginning and end of the print provides visual clues to the direction of movement. “Clear differences in appearance were observed in the starting and ending impressions deposited on absorbent and nonabsorbent surfaces,” says Tate. “Starting impressions on absorbent surfaces were more well defined than ending impressions. In contrast, on nonabsorbent surfaces, the ending impressions were more well defined than respective starting impressions.”
Previous research of latent print distortion has not specifically examined distortion of prints on porous surfaces. “Our paper contributes to the body of knowledge on latent print distortion, and on a practical level, hopefully helps latent print examiners who deal with this on a daily basis understand what’s going on with the casework in front of them,” says Tate.
The paper’s authors are all latent print examiners with the Onondaga County Center for Forensic Sciences in Syracuse. In addition, Tate and Eller offer consulting services through their own firm, Eureka Forensic Services, and teach courses in latent print analysis in SU’s FNSSI program. “Our students enjoy being taught by working professionals who bring our practical experience and our research into the classroom,” says Tate.