ANALYSIS AND COMPARISON OF

HANDWRITING SAMPLES TO

AUTHENTICATE A SIGNATURE OR DOCUMENT

by Joelle Steele

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Handwriting is so unique that it can be analyzed. This is because all children learn to print or write cursive by copying the same models of letters. But each child copies just a little bit differently. Over time and with use, those differences become more pronounced until, by the time we are teenagers, our ability to write is automatic. As adults, our handwriting is unique to each of us. As we age, our handwriting changes under stress, with different health issues, etc., and continues to evolve and change right up until the day we die.

Among the many handwriting traits that can be analyzed are slant, speed, size, spacing, pen pressure, and position of handwriting on the page, as well as the finer characteristics of each letter, including the cross bars on t's, the dots on i's, and the height and width — even the absence — of loops. No two handwriting samples by two different writers are ever exactly the same, no matter how similar they may appear to be on the surface.

Questions about who wrote a document or signed it must be answered by a handwriting expert who compares and analyzes handwriting samples to get to the truth. The handwriting expert who compares known, legitimate signatures with handwriting that is allegedly written by the same person, or that is suspected of being a forgery, is known variously as a handwriting analyst, a forensic graphoanalyst, or in some instances, a document examiner.

Before analysis or testing of handwriting can be done, a handwriting analyst must obtain known, authentic samples of handwriting for use in comparison. These documents are called " standards" or "exemplars." Without them, the handwriting cannot be authenticated. Graphoanalysts usually look for known documents which are similar in content, format, and wording to the questioned one. For example, if they are analyzing and authenticating a signature, they will want exemplars of known signatures. Cancelled checks and other signed legal or official documents are often used for that purpose.

The handwritten documents being analyzed should ideally be originals. Handwriting that has been reproduced by a photographic process, such as photocopies, microfiche, carbon copies, faxing, scanning, etc., is not generally as acceptable. These duplication processes have improved greatly over the years, but they still prevent an expert from analyzing certain traits such as pen pressure and type of pen used, and some processes may additionally enhance or obscure certain handwriting features. Since it is often the smallest and finest of handwriting features that distinguish one writer from another, it is always recommended that original documents be analyzed.

With all the handwriting specimens needed, the forensic graphoanalyst then begins the detailed process of authentication. Most handwriting experts only require their eye to analyze handwriting. So if other analyses are required by a client, the handwriting expert will likely have a battery of preliminary tests done to check for such things as erasures, changes in ink, age of paper, secondary imprints, and any forms of alteration to the physical document. These tests may include highly sophisticated processes such as infrared viewing to detect chemical erasures and changes in the writing instrument; ultraviolet viewing to detect reflections and absorptions; visible filter viewing to detect ink or other absorptions or reflections; infrared luminescence and ultraviolet fluorescence viewing (electromagnetic techniques) to detect non-visible reflections and absorptions; and side or oblique lighting or electrostatic detection apparatus (ESDA) to detect imprints or secondary impressions on pages under the original. Heat can also be used to double-check some of the previous tests, but it is used infrequently because it permanently alters the document.

Once these preliminary tests are run, the analysis of the handwriting may be performed. The graphoanalyst first examines the known and questioned documents to determine that there is only one writer of each, after which a comparative analysis is made to see if the two writers are one in the same or if they are two different people. If the writers are two different people, there could be a forger at work, particularly in the case of checks and wills. But names signed on the backs or fronts of photographs can be simply someone identifying the person in the photograph with no intent to forge that person's handwriting. I personally own at least 50 family photos from the 19th century that are not signed by the person in the photo and do not even identify the person in the photo, but are instead the name of the person who ordered the photo or paid for it or requested copies of it.

The final decision as to whether a signature or handwriting is authentic is often determined using mathematics and probability theory. This is done using formulas based on the number of features found in a given number of letters within a writing sample. These formulas eventually break down into an odds ratio such as 1:368,349,225,981, translated as one chance in 368,349,225,981 that the writer of the document or signature could possess the exact same handwriting characteristics as those of the original writer. In this example, the theory of handwriting uniqueness would be proved since it is so unlikely that any two writer's could possess so many of the exact same handwriting characteristics. Therefore, both the exemplar and the alleged document or signature were likely written by the same person and the alleged handwriting sample was authentic.

A forensic handwriting expert must always have a very well-trained eye combined with extensive training in handwriting styles and letter forms. How well they can authenticate a handwriting sample or signature is otherwise determined by the handwriting itself and the number of exemplars available for comparison.

This article last updated: 03/04/2011.