1. A method performed by a computing device for detecting presence of an illuminated graphical display of a mobile device within a motor vehicle, the method comprising: capturing, by a camera, an image of the vehicle being operated on a public roadway responsive to satisfaction of a trigger condition indicating presence of the vehicle; receiving the image of the vehicle being operated on a public roadway captured by the camera; determining a location of a driver's seat region of the vehicle corresponding to a darker geometric region within the image that is representative of a window of the vehicle; searching within window of the vehicle within the image for pixels of a signature pixel characteristic having a high luminosity relative to other pixels of the darker geometric region and/or a characteristic hue within a predefined range; identifying an area of contiguous pixels of the signature pixel characteristic within the image indicative of the illuminated graphical display of the mobile device; determining whether the area of contiguous pixels appears within a border of a trapezoidal shape having an aspect ratio that is within a predetermined range of a target 4:3 aspect ratio; and outputting an indication of a positive detection of the illuminated graphical display of the mobile device within the image if the aspect ratio of the border of the trapezoidal shape is within the predetermined range of the target 4:3 aspect ratio.