Digital Photographs: Realistic Size Conversion System for Forensic Fingerprint Processing

• Published in: Journal of forensic identification Vol. 71; no. 2; pp. 142 - 162
• Main Authors: Chibel, Ron, Mero, On, Sirota, Noam, Mizrachi, Roy, Eliyahu, Dikla
• Format: Journal Article
• Language: English
• Published: Alameda International Association for Identification 01.04.2021
• Subjects: Automation; Digital photography; Fingerprinting; Forensic sciences; Identification systems; Image processing systems; Software utilities
• ISSN: 0895-173X

Fingerprint images can be processed and searched in an automated fingerprint identification system (AFIS). When inputting an image into an AFIS, the camera does not record the distance between the camera and subject. Because the camera lens and its distance from the target define the size of the framed area, data translation of a digital image file often contains false size measurements. Using a camera with a specified distance between the lens and the object synchronized with the standard AFIS image size can solve this problem; however, it is less suitable in field usage because it is impossible to predict the frame area of fingerprints or handprints at a crime scene. Currently, crime scene investigators use a supplemental scale-bar sticker placed adjacent to the exposed fingerprint prior to photographing the fingerprint. Through the use of photo editing software, the rescaling of the image enables synchronization of the fingerprint's digital size with its actual size (known as 1:1 ratio). In this study, software was specially designed to read special scale-bar stickers and resize the digital images to the original size of the object. The software is also able to accurately transform images captured at an angle of up to 20° from perpendicular to correct for crime scene images where perpendicular imaging is not possible. The software automates and shortens the processing time significantly. The software was tested using 500 different test images, as well as operationally in a nationwide one-year trial. The software proved to be superior to the use of standard photo-editing software and is now available for other crime scene laboratories.