There are three sources of mistakes in patents.  First, the draft of the patent.  Second, changes or concessions made to the claims during prosecution.  Third, external events that are not related to the drafting or prosecution, but which nevertheless degrade or destroy the patent.

Common mistakes 1 – 9 below refer to mistakes that appear on the face of the patent.  These mistakes may have occurred in the original draft, or by changes in the prosecution process.  Common mistake 10 – External Events that Destroy Patent Value, is not an error in the patent itself, but is included nevertheless because of its importance and for the sake of painting a complete portrait.