Forgery is a double process, involving the adoption of another person's writing habits and the relinquishing of one's own acquired habits. The detection of forgery depends on both the forger's skill and the document expert's ability in detection. In trying to cover up defects in the forgery, the forger often overreacts so abnormally that the product becomes even more fraudulent than it was before. Lack of efforts to cover defects does not necessarily indicate that a document is genuine, however, as illustrated by a case example involving forged ballot papers. Handwriting is an applied science consisting of optics, physiology, and psychology. Handwriting strokes in a forgery are slowly drawn as well as clumsy and tremorous. They show halting due to pen pauses as well as careful junctions to hide lifts of the pen. Retouchings can make strokes appear more like pen paintings than like normal writings. A case involving a disputed signature shows 11 differences between the genuine signature and the forgery. An appendix presents a photocopy of the signatures discussed.