No two signatures--even ones penned by the same person-are exactly the same. But some characteristics, such as the writing direction and the way two lines overlap, will remain similar among many samples written by one individual. Traditionally, handwriting analysts have studied scrawls in two dimensions. Giuseppe Schirripa Spagnolo and his colleagues at the University of Rome Three in Italy, have turned up the heat. By scanning a document with laser beams, the team can generate a hologram of the pen strokes within a signature. Using image processing and virtual reality makes it easy to detect the presence of bumps at crossover points, Schirripa Spagnolo says. Finding these bumps allows experts to easily determine the sequence of strokes in a piece of handwriting and the telltale signs of a forgery or original.
The researchers report in the September issue of the Journal of Optics A that the technique correctly verified the author of a signature by comparing it to a set of standards in all 25 samples written with ballpoint pens on regular paper. They also tested handwriting composed with a variety of writing instruments, from felt pens to fountain pens, on other types of paper such as checks and cardboard. Overall, the success rate was nearly 90 percent. Schirripa Spagnolo remarks: We believe this type of 3D micro-profilometry is one of the most promising ways of detecting forged handwriting and it will be a powerful tool for forensic experts around the world.