There are four major approaches (each approach is a group of methods) used for dating inks on documents:
1. Ink Aging Approach
Various methods have been published to measure aging processes that occur in ink on documents.
Dr. Aginsky is the author of two ink aging methods that analyze ink volatile components (not ink dye components*) and that have been tested and applied to actual cases by multiple forensic laboratories. These two ink aging methods are the Sequential Extraction Technique (SET) and Solvent Loss Ratio Method (SLRM). The SET and SLRM measure certain ink aging parameters of ink that decrease as ink ages on paper. Other ink entries are not necessary for comparison.
Dr. Aginsky has developed the SET as a result of many years of research of the ink aging methodology developed and published by Dr. Antonio A. Cantu in the 1980s. To date, the SET is the only ink aging method that has shown its reliability through outside proficiency testing using “blind” samples (outside proficiency tests in 1995, 2001, and 2011).
2. Ink Availability Approach
The second ink dating approach analyzes the chemical composition of inks on a contested document with the aim to determine whether these inks (as well as other materials used to produce the document – paper, inkjet printing ink, toner, stamp pad ink, etc.) were commercially available on or prior to the date appearing on the document.
For example, if the questioned document’s date precedes the manufacturing date for the ink used to sign the document, it is established that the document could not have been signed on the date it bears.
3. Ink Comparison Approach
3.1. Intra-comparison of various written entries in a file or document – The examination’s purpose is to assess whether the entries being compared were produced with the ink of the same composition or with different inks (pens). Such intra-comparisons of inks may reveal that the questioned entries were not written contemporaneously with the other entries in the file (document).
3.2. Comparison of multiple questioned entries dated over a long period of time – The examination’s purpose is to assess whether the use of various inks on the document(s) fits a pattern that is either consistent with the dates appearing on the document(s) or indicates preparation "at one time" (during a short period of time).
3.3. Comparison of the contested document to other similar documents from the same time frame – If other similar documents from the same source and pertinent time frame are available for comparison with the contested document, then:
- The presence of the same printing defects on the contested document and comparison documents (or the same patterns of trash marks or incidental marks on photocopies or laser prints) may yield valuable information concerning the dating of the contested document.
- The physical (optical) and chemical examinations of writing inks, as well as other materials used in the production of documents (paper, inkjet printing ink, toner, typewriter ribbon ink, carbon paper ink, stamp pad ink, etc.), can provide important information as to when a contested document was made.
4. The order of execution of certain elements of a document
Writing ink sequencing – Examining intersections (areas where two or more pen lines cross) to determine the order of writing (it may prove that a particular entry was added at a later time)
Sequencing of indented impressions and writings – Examining intersections (areas where the visible ink lines cross the indentations) may determine the order of writing and thus prove that a particular entry was added at a later time.
Paper folds – It is often possible to determine whether an ink line that intersects a paper fold was written before or after the paper was folded.
Offset marks – When two pieces of paper are pressed together, marks such as writing (and printing) may be transferred from one to another. When the writing on the reverse side of a sheet of paper in a bound ledger intersects with the writing on the front side of the sheet of paper, ink may be transferred from the front page onto an underlying page. Such transfers will occur only when inks are freshly applied. For example, if transfers of ink are found on several pages of a diary, it indicates that the corresponding entries on the diary were made in a single sitting, not over a longer period as suggested by the dates.
Ink and Toner Intersections – When a signature (or a handwritten notation) intersects a printed text on a document, a forensic document examiner may be asked which came first, the text or the signature (handwritten notation). The answer to that question may determine whether the document has been altered (by adding certain information).
It should be noted that sequence of execution may be determined even when lines of the text and signature (handwritten notation) do not intersect. For example, a forensic document examiner can determine whether the stray toner particles (they are present on any laser-printed and photocopied documents but invisible to the naked eye) are below or above ballpoint pen ink writing (see Aginsky, V.N., “Determining the Sequence of Non-Intersecting Media on Documents: Ballpoint Pen Ink and Laser Toner Entries,” Journal of the American Society of Questioned Document Examiners, Vol. 5, No. 1, 2002, pp. 1-4).
* At present, the ink aging methods that analyze ink dye components are considered unreliable by the overwhelming majority of ink dating specialists and forensic document examiners.