The use of copies offers a number of advantages to persons engaged in certain types of crime. Examples of cases include anonymous letters, leakage of confidential information, false insurance certificates, and the preparation of composite documents from parts of various genuine documents. Photocopy processes are explained in detail. The two main categories of processes are the direct process and the indirect process. Any examination of copies must start with a determination of which of these two processes was used. Other steps in the examination include a chemical analysis of the toner and a comparison of defect marks in the photocopy process. The discussion concludes that glass defects are the only permanent defect marks on a copier that will be consistently reproduced on copies. While the presence of the same defect on two documents will indicate common origin, the absence of a defect on one, although present on the other, does not necessarily indicate that the documents were copied on different machines. The interpretation of the absence of defects from particular documents must be approached with caution and requires a detailed knowledge of the mechanism of the particular machine in question. The expected increase in the use of color copiers will pose a future challenge for forensic scientists. Diagrams, illustrations, and six references are supplied.