Jornal de pesquisa forense

The Variability Measurement of Shape Independent Features to Establish a New Method to Differentiate Genuine Signatures from Simulated Ones

Abstract

Fausto Brugnatelli

A preliminary step to the examination of signatures is the objective assessment of the variability range that is peculiar to the writer; in document examination it is quite rare to come across standardized procedures allowing an effective discrimination between genuine and simulated signatures. This study took into consideration 104 questioned signatures (coming from 20 real and Judge-ruled cases) that were inspected to evaluate non-shape-related indicators in their ability to assess correctly genuineness or simulation; the research particularly focused on the evaluation of letter heights - with special reference to the positions of the individual letters within the signature - and on the subsequent height ratios between extenders (upper and lower) and the other small letters. The combination of the information gained from the statistical survey, assisted by calculation of confidence intervals, of these height indicators with the observation within the signature of the spots where between-letter pen lifts occur led to an effective discriminating method for medium/long signatures. Data processing also yielded useful indications on the letters that most frequently trigger off height errors in forgery and provided other interesting results, such as the positions within the signature where simulators most frequently fail.