It has been said that any two objects larger than molecular size contain variation. And so it is with handwriting. We never write anything exactly the same. Every time we write, our writing is slightly different. Sometimes a little larger, sometimes smaller, faster, slower, more angled, less angled, and on, and on. Our individual characteristics will be slightly different each and every time we pick up a pen.
The parameters of an individual’s handwriting are defined by these small changes to individual characteristics. For this reason the questioned document examiner may require numerous handwriting specimens to provide a basis for a viable comparison to a questioned writing. The comparison process is not that of determining if two writings are exactly alike, that will never occur; it is a determination of whether the questioned writing or signature fits within the parameters of individual variation exhibited in the standard material.
Simply put, when an ample quantity of handwriting containing a pattern of sufficient unique habitual movements, or individual characteristics, produces a totality of similarity within the parameters of individual variation with another body of writing, it must be concluded that both writings are the product of one person.