Chemical Analysis
It is possible for different inks to react similarly when examined using the Video Spectral Comparator. If VSC results are inconclusive, second-stage testing using a technique called Thin Layer Chromatography (TLC) may be required.
Thin Layer Chromatography: Unlike most other forms of analysis that we use, TLC results in a change to the condition of the document. Small samples of ink-bearing paper are removed, leaving pin-sized holes in the page. These samples, called micro-discs, are chemically processed so that the various components of the ink separate. If the inks being compared show different results, we can conclude that they did not come from the same pen. The findings from Thin Layer Chromatography can be critical to investigations about how and when a document was prepared.
Analysis: In the following case example, a dispute arose between two brothers concerning when they had executed certain trust declarations. One brother maintained that the three declarations were all signed at the same time, with each brother using his own pen. The other brother claimed that two of the three were completed together, while the third was executed later. According to him, during the second signing, one pen was shared.
The Question: We were asked to determine whether the three declarations were signed at the same time, or at different times.
TLC Analysis: Attempts to differentiate inks using infrared analysis were inconclusive. Chemical testing, however, produced definitive results.
The Chart: The differences in ink components can be seen on the TLC plate illustrated on this Chart. Show Me The Chart.
Q1 and Q2 each bear two inks: one for brother "A," the other for brother "B." On Q3, however, one ink is used for both signatures. It is not the same as either ink found on Q1 and Q2. In other words, it is from a third pen.
Conclusion: TLC testing showed that at least three pens had been used; this data best supports the second signing scenario, i.e., the documents were signed at different times.