The Box Effect: Forensic Analysis of Signature Variation Under Spatial Constraint

The present study examines the “box effect” in forensic document examination by evaluating the influence of spatial constraints on English script signatures. A total of 1000 participants (500 males and 500 females), aged 15–75 years, provided paired signature specimens. Each participant produced signatures under two conditions: within a predefined box and on an unconstrained blank space. All specimens were created using the same writing instrument and paper quality (75 GSM). Handwriting characteristics were analysed at both macro and micro levels, including signature dimensions, spacing, slant, alignment, and initial and terminal strokes. Since the dataset comprised paired observations, statistical analysis was performed using McNemar’s test. In addition, a Random Forest model was applied to classify signatures based on writing conditions and to identify the most discriminative handwriting features affected by spatial constraints. The findings indicate systematic variation in signature characteristics under constrained conditions, particularly in terms of dimensional reduction and alterations in slant and stroke execution. The study highlights the forensic significance of understanding natural variation in signatures executed under imposed spatial limitations, contributing to the evaluation of questioned documents where signatures are produced within fixed boundaries