APPROACH TO ESTABLISHING THE AUTHENTICITY OF DISPUTED SIGNATURES WHICH IS IN ACCORDANCE WITH THAT PRESCRIBED BY THE INTERNATIONAL ASSOCIATION OF STANDARDS AND METHODS (ASTM) E1658-04) – SPECIAL WORKING GROUP OF DOCUMENT EXAMINERS (SWGDOC):
In order to ascertain whether or not disputed signatures are authentic, an adequate number of acknowledged signatures would be necessary for use as standards for comparison purposes.
The quantity of standards required would depend on the overall consistency of the writer’s normal signature; natural variation is bound to occur in everybody’s signature. A larger number of standards would be necessary if the writer has a tendency to vary his/her signature considerably.
The best standards would be the signatures written spontaneously on documents contemporaneous with the disputed signatures, and preferably those appearing on documents similar to the questioned documents.
Request specimens, where the writer is asked to produce exemplar signatures, are of less value for comparison purposes than are collected specimens as described above. However, if the specimens submitted differ significantly from the collected specimens, this would suggest that the writer is being deceitful.
Generally the examiner should not be deceived by self-serving standards.
The standard of writing capability demonstrated in the known and disputed writings would be compared. It is axiomatic that a person cannot write beyond his/her ability or skills.
The line quality, including the evenness of the line as well as the pressure pattern, would be compared. Hesitation, tremor, and inappropriate pen lifts occurring within the line would be sought.
Consistency in the overall spontaneity demonstrated by the speed and fluency of the line would be investigated; for example the occurrence of tapering flying starts and finishes of lead and end strokes,
The slope, the alignment of the signature’s components with the given or presumed base line, the positioning of pen-lifts and line re-starts, the line direction and the sequence of strokes, the spacing between letters and strokes, the positioning of the “i” dots and the “t” bars, the proportional height of the short and tall letters, the positioning of the apices of the tall letters, the writing pattern at the top and at the bottom of the signature, would be compared.
Generally, common individual characteristics occurring among the letter formations would be sought.
Persistent dissimilarities that could not be argued away as natural variations would be sought.
Latent guide lines and grooves within the line, coupled by the lack of spontaneity of the line, would be investigated regarding the possibility that the signatures were traced.