Abstract
A cardinal tenet of forensic document analysis is that the existence of a single fundamental difference between questioned and known handwriting samples is a basis for excluding the samples as having come from a common source. But applying that doctrine to actual cases can be difficult because of different interpretations as to what constitutes a true fundamental difference. A review of the literature reveals that there is not just a single classification of a fundamental difference. When differences are observed between writing samples, an additional difficulty occurs in determining whether the suspect can be “eliminated” as the writer, or whether the examiner should merely report that “there is no basis for identifying the suspect as the author.” The critical element in the analysis is in determining what constitutes a reasonable explanation for the observed characteristics. Circumstances that may lend themselves to varying interpretations of how fundamental are any observed differences include situations in which: (1) a single feature or letter differs between the questioned and known samples; (2) the format of the samples contrasts cursive handwriting with manuscript handprinting; (3) the questioned writing exhibits poorer line quality than the known writing; (4) there is only a small quantity of known comparison standards; (5) the writer has used a disguise that may cause the writing samples to appear to be fundamentally different.
