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Strengthening Forensic Science in the United States: A Path Forward
origin. Ink comparisons usually are performed to answer four basic categories of questions: (1) whether an ink is the same (in formula) as that on other parts of the same document or on other documents; (2) whether two writings with similar ink have a common origin (e.g., the same writing instrument or ink well); (3) whether the ink of entries over a period of time is consistent with varying ages or indicates preparation at one time; and (4) whether ink is as old as it purports to be.
Most problems with ink examinations arise from confounding factors that interact with the ink. These can be part of the writing process, such as blotting wet ink; variations in the papers; various forms of contamination on the document; or a combination of these factors. Most ink examinations must be performed on paper and without defacing the handwriting, and this creates a number of sampling and analytical challenges.
The examination of handwritten items typically involves the comparison of a questioned item submitted for examination along with a known item of established origin associated with the matter under investigation. Requirements for comparison are that the writing be of the same type (handwritten/cursive versus hand printed) and that it be comparable text (similar letter/word combinations). Special situations involving unnatural writing are forgery (an attempt to imitate/duplicate the writing of another person) and disguise (an attempt to avoid identification as the writer). The basis for comparison is that handwriting/handprinting/numerals can be examined to obtain writing characteristics (also referred to as features or attributes). The characteristics are further classified into class characteristics (the style that the writer was taught), individual characteristics (the writer’s personal style), and gross/subtle characteristics.
Specific attributes used for comparison of handwriting are also referred to as discriminating elements, of which Huber and Headrick have identified 21.96 Comparisons are based on the high likelihood that no two persons write the same way, while considering the fact that every person’s writing has its own variabilities. Thus, an analysis of handwriting must compare interpersonal variability—some characterization of how handwriting features vary across a population of possible writers—with intrapersonal variability—how much an individual’s handwriting can vary from sample to sample. Determining that two samples were written by the same person depends on showing that their degree of variability, by some measure, is more consistent with intrapersonal variability than with interpersonal variability. Some cases of forgery are characterized by signatures with too little variability, and are thus inconsistent with the fact that we all have intrapersonal variability in our writing.
R.A. Huber and A. M. Headrick. 1999. Handwriting Identification: Facts and Fundamentals. Boca Raton, FL: CRC Press.