The Effects of Constraint on a Signature’s Static and Dynamic Features

Forensic document examiners are tasked daily with determining the authenticity of signatures. The majority of these signatures are found on a line, within a box or within text. A major concern with this type of examination is the presence of these lines, boxes and text, since they can pose a form of constraint resulting in variations to an individual’s natural signature. This study examined the effects of constraint on an individual’s signature with the use of a digitizing tablet and inking pen to measure both the dynamic and static characteristics of the signature. Forty participants ranging in age from 16 – 83 provided a series of signatures for a total of 2400. Each participant signed in the presence of five different constraints, mimicking actual Canadian Government forms, including: a 4.7 cm line, a 6 cm x1.2 cm box, a 4.8 cm x 0.96 cm box, a 6.4 cm length and 0.4 cm height space within text, the Adult General Passport Application box produced by Passport Canada and a blank sheet as a control. This study suggests that when constraint is introduced, the pen speed, pen jerk, overall length, ascenders and descenders all vary significantly from that of the unconstrained signature. Pen pressure was the only feature to not show significant difference in the presence of constraint. In addition to these dynamic characteristics, anomalies such as extra artefacts, variation in complexity, hesitations, health issues and signs of anxiety were observed. This study demonstrates the impact that constraint has on a signature and indicates to forensic document examiners the need to carefully consider and evaluate these variations in the examination process.