What Factors Affect Forensic Document Examination?

By Georgios Christofidis, Ph.D.Reviewed by Emily Henderson, B.Sc.

What is Forensic Document Examination?

Currently, the most intriguing topic of forensic document examination is the accurate dating of documents. The dating of documents is defined as determining when the document was formed or produced. This feat can be accomplished using many different techniques, such as ink analysis (both written and printed), type of paper analysis, watermark analysis, and elemental analysis. Other frequently used methods include handwriting examination, determination of the sequence of intersecting lines, printing method identification, and particle analysis.

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Ink Analysis

Among all the techniques mentioned above, dating has been potentially mastered by employing ink analysis. Documents can generally be dated using two methodologies; (1) static approach and (2) dynamic approach. The static approach focuses on analyzing the document’s constituents (ink, paper, and toner) and their first date of introduction into the market, which makes them available to the public. It gives the time frame when the document could have been formed, wherein the earliest ‘’border’’ of that time frame is the year the constituents in question were first inducted into the market.

There are two key points when dating documents through a static approach: (1) the parameter analyzed should not vary with time (i.e., certain compounds that can be found when analyzing the chemical composition of ink). (2) An extensive database should be available having all analyzed parameter and their date of introduction.

Databases like that are available, such as the US Secret Services’ International Ink Library or the Zurich Police Reference Ink Collection. When employing static methods, certain aspects must be carefully considered. While interpreting introduction dates, it should be kept in mind that the same products might be inducted into the market much later in different geographical locations; for example, the gel inks were introduced in Japan in 1984, but in the US, they were not made available in the market till the later years of the same decade.

On the other hand, the dynamic approach focuses on the analytical examination of the constituents of a document (ink, paper, and toner) and monitors their change over time by closely examining their aging process. Due to ink aging being more researched, dynamic approaches focus more on ink aging than paper aging. However, some research is being carried out to better understand the paper aging process and employ it for dating.

The analytical techniques usually employed for static ink analysis are HPLC, HPLC-DAD, FTIR, TOF-SIMS, and Raman Spectroscopy. GC-MS, SPME/SPME-GC-MS, and thermal desorption coupled with GC-MS are usually employed for dynamic ink analysis.

Paper Analysis

The same line of thinking used for ink analysis can be adopted when analyzing paper. When using the static approach, information such as when the urea-formaldehyde resin was first used as a coating on paper or when paper with optical whiteners was first introduced to the market can be useful.

All these different components can be determined using well-established analytical techniques such as UV, fluorescence, Gas Chromatography, or even Thin layer Chromatography. There are also some databases available regarding watermarks, which can aid in reaching the manufacturers and finding out when the specific watermark was used for the first time. When using the dynamic approach, the focus would be on paper aging. This is a more challenging topic because paper starts aging immediately after it is made, therefore not providing a clear time frame for when the document was actually created.

However, techniques such as pyrolysis-GC-MS are used for samples about 30 years old. Other tests to determine the age of paper include mineral determination by spot tests, acidity, and nitric resistance of paper.

A New Perspective in Forensic Document Examination?

Very recently, in a study by King et al., a new method was employed which makes possible the elucidation of the order of deposition of ink and fingermarks on a questioned document, also known as ‘’determining the handling sequencing’’. This was achieved by using well-established techniques in a novel way, specifically by combining forensic gelatin lifters with a development chamber that utilizes the disulfur nitride polymerization on fingermarks.

The latter was initially designed to retrieve fingermarks from metallic surfaces subjected to extensive washing, but it turns out that it allows the visualization of surface interactions on gelatin lifts. In the same study, they concluded that when a fingermark had been deposited on top of the block of ink, it could be clearly developed using the combination of the abovementioned techniques.

However, clear development was not possible for fingermarks that were deposited prior to ink placement by a laserjet printer. Although only one study has produced favorable results on this research topic, this new approach provides clear evidence that this type of essential information can be extracted when analyzing a document of interest.

A Step Forward

Despite the availability of multiple sophisticated techniques for forensic document examination, the actual dating of documents in routine forensic casework remains elusive due to their cost and high maintenance requirement. Additionally, all these dating methods would need to be validated individually and in conjunction with one another; this can be a huge task.

When it comes to further research on the matter of determining the handling sequencing of a document of interest, more research on analyzing documents of inkjet printers and the effectiveness of this new approach with inkjet deposition mechanisms would be beneficial, along, of course, with different deposition methods such as stamps or written ink.

Further Reading

• All Forensics Content
• Collecting Evidence at a Crime Scene
• Using Forensics to Tackle Child Exploitation
• Forensic Investigations of Natural Disasters
• Forensic Identification in Mass Disasters