The identification of the machine either photocopier or drum can be made by observing the defects over the copies generated through the machine. These defects are called as trash marks. These trash marks are because of the dust and dirt particles present inside the machine. They may also appear as a result of defect in the machine parts.
These particles can be seen as dark specks on the copy. If the suspect and the sample photocopied document have the same trash marks then this can be said that they have been generated from the same machine. The size, color, shape and groupings of these markings can be compared and matched to establish the link between the two or more comparable documents.
