When two pen strokes intersect in a signature, can we determine which was written first? The answer may be significant in a disputed document, but the intersection is not always as straightforward as it appears.

We recently assisted a law firm in examining a stroke sequence argument involving the signature of a deceased person. The matter illustrated how the choice of optical method can influence an examiner’s observations and, ultimately, an opinion presented to the court.

Magnification is only one part of the examination

A handheld microscope can enlarge a stroke intersection and reveal details that are difficult to see with the naked eye. Magnification alone, however, may provide insufficient information to determine the order in which the strokes were made.

Where ink deposits overlap, a darker or heavier deposit can appear to be the uppermost stroke. That appearance can be misleading: a stroke that looks as though it was written last may, in fact, have been written first. An examiner should therefore avoid treating apparent darkness at an intersection as conclusive evidence of sequence.

What a change in illumination can reveal

Examining the same intersection under lighting from different angles can reveal surface details that are less apparent under ordinary magnification. Depending on the document and writing materials, relief imaging and other suitable optical methods may provide further information about the construction of the strokes.

The images below show the same stroke intersection captured using two methods. The left image was obtained with a digital negatoscope; the right image was captured with a handheld portable microscope. Their different appearances demonstrate why observations should be assessed using appropriate methods before a conclusion is reached.

The same stroke intersection viewed using a digital negatoscope (left) and a handheld portable microscope (right). The images illustrate differences in visible detail; they do not, by themselves, establish the stroke sequence.

A conclusion must be supported by the evidence

Stroke sequence examination calls for more than access to an optical device. The examiner must select methods suited to the question, understand what each method can and cannot reveal, and interpret the observations in the context of the original document.

Training provides a foundation. Sound method selection and the competence to assess the resulting evidence are equally necessary, particularly when an expert opinion may be relied upon in court.