An optical scanner scans a first portion of a print of a body part such as a finger in a first area of an optical surface. The optical scanner detects a motion of the body part to a second area of the optical surface. This can be done in various ways. One way is for the optical scanner to detect a sliding motion of the body part to determine if most of the first portion of the print is in the second area. Another way is for the optical scanner to determine a rolling motion of the print based on a continuity of the print from the first area to the second area. A similar system and method is disclosed which detects a rolling motion of a body part by using a sleeve with multiple properties.