Paper as evidence

DEFINITION: Flexible sheets of compressed wood pulp, or similar substrates made of other materials, used chiefly for written and printed documents but also for disposable containers.

SIGNIFICANCE: Paper most commonly figures as evidence in civil forgery cases. Many of the tools that forensic scientists use to analyze inks and toners can also be applied to the paper on which these substances appear. Questioned document analysts focus more attention on ink and handwriting than on paper because the writing itself usually provides more definitive clues than the substrate. The analysis of paper, however, can be crucial to proving forgery or the authenticity of works of art and historical documents. In addition, fragments of paper found at crime scenes may provide evidence that can link suspects to crimes.

A piece of paper, independent of any writing or printing that may appear on it, conveys a wealth of information. By examining it closely, an expert can often tell where and when it was manufactured. Telltale signs of its subsequent history—how it was stored and whether it was treated in any way—may be discernible as well. Forensic scientists may also be able to match paper fragments that have been torn or cut from larger original pieces to those original pieces in a process known as fracture matching.

Differing Characteristics

Paper manufacturing originated in Asia and was imported into Europe in the late Middle Ages. Paper is basically a felt made of plant fibers compressed to form a thin, tough sheet. Certain characteristics imparted by the papermaking process are visible in the finished product. These include the species of plant from which the fibers were derived, the chemical and mechanical means used to extract and treat the fibers to make them suitable for papermaking, bleaching agents and dyes, density, surface texture imparted by rollers, watermarks, fillers, and substances used for coating.

The older the paper, the more likely the species of plant used in its manufacture is to be diagnostic. In the twenty-first century, wood chips used in pulping are shipped all over the world. In contrast to new paper from large international conglomerates, which varies little in its species composition, recycled paper can be highly diagnostic because the species mix changes so much from batch to batch.

Because visible surface features of documents can be photocopied, many firms and government agencies print their most sensitive documents on security paper that is manufactured for specific purposes. Such paper incorporates fibers, watermarks, invisible reactive inks, and other features that forgers and counterfeiters cannot reproduce without access to the original, tightly controlled paper stock.

Analysis Techniques

Document analysts use radiocarbon dating as well as the analysis of paper manufacturing techniques to determine the ages of old documents and drawings. Serious forgers of purportedly old documents attempt to avoid discovery by using antique paper. In the initial authentication of the Vinland map, which was claimed to be a fifteenth-century copy of a thirteenth-century map proving Viking settlement in the New World, investigators concluded that the map was genuine because it was drawn on fifteenth-century parchment. A supposed center fold, however, turned out to be a seam where two leaves were joined before the map itself was drawn. Through microscopic examination, forensic document examiners can readily determine whether folds or mechanical damage on a piece of paper occurred before or after the paper was written on. Something written after the paper was damaged raises suspicion of forgery.

The origins of the fibers used in paper can be determined through examination of the morphology of individual fibers with either transmitted light or scanning electron microscopy (SEM). Forensic scientists use the same spectrographic methods they apply to analyzing ink in analyzing paper. SEM produces a high-resolution image of surface features, and a laser-scanning confocal microscope produces a three-dimensional image. As an adjunct to SEM, energy-dispersive spectroscopy (EDS; also known as energy-dispersive X-ray spectroscopy, or EDX) measures the X-ray emission spectra of compounds bombarded by electrons. An EDS reading indicates which atomic elements are present in a sample and in what proportions.

Infrared absorption spectrometry detects specific types of chemical bonds in organic molecules. This technique is useful for detecting coating agents on paper and for tracing plastics used in place of paper. Photographic papers often have distinctive chemical signatures and surface characteristics. Trace-element analysis using plasma has been used to identify batches of recycled paper. Examination under reveals erasures and stains, and raking (low-angle) light shows buckling and watermarks.

A discarded paper match found at an arson scene or at another kind of crime scene can be a valuable piece of evidence. If investigators identify a suspect and find in that person’s possession the matchbook from which the discarded match came, the torn end of the match will correspond to the stub in the matchbook. Also, because paper matches are made from recycled cardboard, the lot number and its distribution pattern can be determined from the fiber content of the match. This information can provide investigators with a range of places where the suspect might have been seen immediately prior to the commission of the crime.

Although paper analysis has entered into a number of high-profile historical criminal cases, notably in the analysis of the ransom notes in the 1932 of Charles A. Lindbergh’s infant son, the findings of paper analysis are rarely definitive. An exception is the hoax involving diaries purportedly written by Adolf Hitler, in which the handwriting, writing style, and supposed origin of the documents were plausible, but analysts determined that the paper itself could not have been manufactured before 1950.

Bibliography

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Kapoor, Neeti, et al. "Forensic Analytical Approaches to the Dating of Documents: An Overview." International Microchemical Journal, vol. 170, Nov. 2021, doi.org/10.1016/j.microc.2021.106722 Accessed 16 Aug. 2024.

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