An objective look into the effect of inversion and legibility on signature simulation difficulty

In the push for more objectively based evidence in support of forensic document examination practices and theory, new empirical studies with novel methodologies are emerging. Until now, estimating the difficulty of a forgery has been primarily derived through evaluation of the quality of the simulation, rather than through forger‟s objective behaviours. The current study investigated the difficulty of simulating a legible and illegible signature by examining the gaze-behaviours and pen kinematics of forgers. Twenty subjects‟ eye and pen kinematic movement behaviours were recorded during simulations of an exemplar signature presented in an upright (legible) and inverted (illegible) orientation. We found that signature orientation greatly impacted upon the simulators‟ gaze and kinematic behaviour. Between the two conditions there was a significant difference in the pen-down writing time (p=0.003), pen in-air time (p=0.029), penpressure (p=0.0002) and exemplar gaze dwell times (p=0.0054). However there was no significant difference in pupil size (p=0.72). These findings help us better understand how inversion and legibility can affect the ability to simulate a signature. These findings have implications for the forensic examination of these features in questioned signatures and may also be of interest to those wanting to understand more about the physical aspects that contribute to rendering signatures less vulnerable to forgery.