Document examination in criminal investigations

DEFINITION: Application of analytical techniques to questions of the authenticity or origins of materials that bear marks, signs, or symbols that have meaning or convey messages.

SIGNIFICANCE: An important component of forensic science is the investigation of questioned documents, which may be anything from written death threats to ransom notes to suicide notes to adulterated wills. The analysis of documents can help to connect suspects to such crimes as kidnapping, bank robbery, and forgery.

In the forensic science field of document examination, anything that bears marks, signs, or symbols that have meaning or convey messages is considered to be a document. Document examiners establish the authenticity or inauthenticity of contested materials, detect alterations in documents, and trace documents to their places of origin. Among the tasks performed by document examiners are handwriting comparisons, comparisons of type styles, ink analyses, and comparisons of documents created using typewriters, fax machines, and computer printers.

Handwriting Identification

Handwriting analysis is conducted in many types of investigations, including cases of fraud, homicide, suicide, drug trafficking, sexual offenses, threats, extortion, blackmail, arson, and robbery. No two individuals have the same handwriting style; each person’s handwriting displays unique features that distinguish it from the writing of all other persons. Among the features of handwriting that differ from person to person are the use of margins; the spacing, crowding, alignment, and slope of letters; the pressure applied to the writing instrument; and the speed with which the writing is done. In addition, document analysts look at related matters such as spelling, punctuation, phraseology, and grammar.

Handwriting analysts compare the handwriting on questioned documents with the handwriting of any identified suspects using authenticated handwriting samples (writing exemplars) obtained from those individuals. Ideally, writing exemplars are produced in a manner that makes them as close as possible to the questioned documents under examination; that is, the size and type of paper and the kind of writing instrument used should be the same, and the same text should be written. The text to be written is dictated to the suspect, and no instructions are given concerning the spelling, punctuation, or arrangement of the requested writing sample.

The writing of several pages of dictation yields exemplars that best represent a suspect’s subconscious style and characteristics. As the amount of writing that a is asked to produce increases, it becomes more difficult for the suspect to conceal his or her own writing style and to imitate the writing style of another. The suspect is also required to provide writing samples from both the right and left hands. In addition, when possible, the analyst compares the requested exemplars and the questioned document against writing examples from the suspect that were produced before that person was officially contacted by law enforcement. Such examples might include business records, personal correspondence, and canceled checks.

Indented Writing

Forensic document examiners are sometimes able to connect suspects to crimes by examining the indentations left on sheets of paper when other sheets that rested above them have been written on, such as on notepads. For example, a bank robbery note may be connected to a writing pad recovered from a suspect’s residence.

The clarity of such impressions is influenced by the amount of pressure that was used by the writer and the thickness of the paper. If the indentations are deep (from heavy pen pressure, for instance), they may be visible to the naked eye. If the indentations are too shallow to be seen clearly, the analyst may enhance them by using the Electrostatic Detection Apparatus (ESDA). This instrument uses a vacuum to seal a thin plastic film over the sheet of paper with the suspected indentations. The plastic film is then given an electrostatic charge, and black toner is applied to it. The toner adheres to any indentations in the paper, making them clearly visible. A sticky transparent plastic film is then placed over the indentation patterns on the paper to preserve them for examination and possible presentation as evidence.

Detection of Alterations

Document examiners sometimes are called upon to detect whether documents have been modified through erasure, addition, or the blotting out of information. One of the most common ways in which documents are altered is through erasure of parts of the writing or type. Whenever a part of a document is erased (whether through use of a rubber eraser, a piece of sandpaper, or a razor blade, for instance), the surface fibers of the paper are disturbed. Microscopic examination of a document can thus reveal whether areas of it have been erased.

Some alterations to documents involve the overwriting or blotting out of segments of text. To uncover text that has been overwritten, a document examiner may employ the Video Spectral Comparator (VSC), an instrument that uses infrared illumination. Different kinds of inks have distinct chemical compositions that reflect light differently, and the VSC highlights such variations in light reflectivity. Differences in the inks that appear on a document are a strong indication that the document has been altered. The VSC is also sometimes able to uncover text that has been overwritten or blotted out because the light reflection of the ink of the text that has been covered up may be discernible under that of the ink that was used to cover it up. If precisely the same ink used in the original document was used to overwrite or blot out text, however, recovery of the original text may not be possible.

Identification of Typewriters

Typewriters have been used in the production of many kinds of questioned documents, from travel papers to wills to terrorist manifestos. In the forensic examination of typed documents, analysts are often concerned with identifying the documents’ sources by determining the makes and models of the typewriters used and when the typed documents were produced. They might also need to determine whether particular series of documents (such as several bomb threats) were prepared on the same typewriter.

Knowledge of distinguishing features among typewriters allows investigators to identify the kind of typewriter used to produce a given document. In many cases, analysts can match a document up with an individual typewriter. Some of the distinguishing characteristics among typewriters that make such identification possible include the typeface that was produced, whether the type was produced by a manual or electric typewriter, whether the typewriter used fabric or carbon ribbon, and whether the type was imprinted with a type bar or with daisy wheel or ball printing elements.

The style of typeface that appears in a typed questioned document is useful for tracking down the make and model of the typewriter, as the typeface styles produced by different makes and models of typewriters are limited. Document examiners can compare the typefaces in questioned documents with typefaces in available databases to identify the makes and models of the typewriters that produce them.

A document analyst may connect an individual typewriter to a document by examining the impressions left on the typewriter ribbon to find the portion of the ribbon on which particular text was typed. In addition, unique features (that is, tool marks) are imparted on documents by the typewriters that produce them, because every typewriter has moving parts that experience random damage and general wear. Such unique features can be used to connect documents to particular typewriters.

Identification of Computer Printers, Photocopiers, and Fax Machines

In cases that involve documents produced by computer printers, photocopiers, or fax machines, analysts may be asked to identify the makes and models of the machines used or to compare questioned documents with samples printed from suspected machines. In conducting such an analysis, an examiner usually produces ten samples from each suspect machine to obtain a sufficient representation of the machine’s characteristics. The examiner then undertakes a side-by-side microscopic comparison of the questioned document and the printed exemplars, focusing on such details as character shapes, the type of toner used, and the method by which the toner was applied to each document.

Different computer printers (including ink-jet, laser, thermal, and dot-matrix printers) have characteristic ways of printing documents. Investigators also look for any tool marks on documents that have been made by the belts, pinchers, rollers, and gears that move the paper through a machine. Many laser printers are designed to mark documents so that documents may be traced back to them. A document analyst may identify the source of a photocopied document by noting defects that are reproduced on copies from the glass platen, lens, or drum of a particular machine. The source of a document produced by a fax machine may be identified by the document’s header, known as the transmitting terminal identifier (TTI). The TTI, which appears at the top of each fax page, identifies the machine that sent the document. Law-enforcement investigators have access to a database of TTI fonts and the corresponding fax machines that use them.

Bibliography

Bennett, Wayne W., and Kären M. Hess. Criminal Investigation. 8th ed. Belmont, Calif.: Wadsworth/Thomson Learning, 2007.

Gaensslen, R. E., Howard A. Harris, and Henry C. Lee. Introduction to Forensic Science and Criminalistics. New York: McGraw-Hill, 2008.

Hicklin, R. Austin, et al. "Accuracy and Reliability of Forensic Handwriting Comparisons." Proceedings of the National Academy of Sciences (PNAS), vol. 199, no. 21, 9 Aug. 2022, doi.org/10.1073%2Fpnas.2119944119. Accessed 14 Aug. 2024.

Kelly, Jan Seaman, and Brian S. Lindblom, eds. Scientific Examination of Questioned Documents. 2d ed. Boca Raton, Fla.: CRC Press, 2006.

Morris, Ron N. Forensic Handwriting Identification: Fundamental Concepts and Principles. New York: Academic Press, 2000.

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