The probative character of Forensic Handwriting Examiners' identification and elimination opinions on questioned signatures.

This 5-year study investigated the character of Forensic Handwriting Examiners' (FHEs) authorship opinions on questioned signatures through the medium of blind validation trials. Twenty-nine thousand eight hundred and eleven authorship opinions were expressed by FHEs on trial kits comprising randomized questioned genuine signatures (written by the specimen writer), disguised signatures (written by the specimen writer) and simulated signatures (not written by the specimen writer). Results showed that, as a group, FHEs were significantly more confident at identifying writers' genuine signatures than identifying writers' disguised signatures or eliminating specimen writers from having authored simulated signatures. It is proposed that the difference in FHE confidence arises from the difficulty they have in deciding which alternative authorship explanation accounts for perceived combinations of similar and dissimilar features between specimen and questioned signatures.