Investigating the Potential for Training Context Effects to Influence Forensic Document Examiners' Relative Skill at Writer Individualization and Exclusion

Abstract

The relative ability of forensic document examiners (FDEs) to provide support for the proposition of individualization or exclusion on the basis of handwriting features was investigated by surveying opinions expressed in case files by one laboratory’s FDEs and comparing this data to blind trial test results taken over a five year period. The survey of FDEs opinions on reports showed that opinions were skewed towards support for writer individualization over writer exclusion 92% of the time. Since historically FDEs develop their skills with respect to individualization/exclusion primarily on case files, it is proposed that this unbalanced training context may skew their abilities to carry out the tasks. To determine one laboratory’s capacity to correctly provide both individualization and exclusion evidence, results of blind validation trials were analyzed. For natural writing written and not written by the specimen writer, FDEs were 62 times more inconclusive when providing support for exclusion of the specimen writer when the specimen writer did not author the questioned sample, than they were for providing support for individualization when the specimen writer wrote the questioned sample. An intriguing possibility is that because of the unbalanced training set, government FDEs may acquire skills which are skewed towards individualization over exclusion.

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