Using Sensor Dirt for Toolmark Analysis of Digital Photographs

Dust particles that collect on the image sensors of digital cameras often leave marks on the pictures taken with these cameras. The question therefore arises whether these marks may be used for forensic identification of the camera used to take a specific picture. This paper considers the question by investigating the impact of various camera and lens factors, such as focal length and recording format. A matching technique involving grid overlay is proposed and the probability of false positive matches is quantified. Initial results indicate that toolmark analysis based on sensor dirt has potential as a forensic technique for camera