Forensic handwriting examiners’ opinions on the process of production of disguised and simulated signatures

Large-scale blind testing of forensic handwriting examiners (FHEs) has shown that authorship opinions on disguised and simulated signatures attract higher misleading and inconclusive rates than genuine signatures do. To test whether this is due to the failure of FHEs to detect the indicators of disguise/simulation behaviours we examined their opinions regarding the ‘process of production’ (which in this case was a choice between written naturally or written using a disguise/simulation strategy) of the questioned disguised and simulated signatures in blinded skill testing trials. The relationship between their process opinions and authorship opinions is then assessed. It was found that the majority of the inconclusive authorship opinions for both disguised and simulated signatures had a correct process opinion (707 of 1241, 57.0% for disguised; 3838 of 4368, 87.9% for simulated), with only 7.3% (90 of 1241) of the disguised and 0.85% (37 of 4368) of the simulated signatures exhibiting incorrect process opinions. For the total misleading authorship opinions relating to disguised signatures, the majority of the process opinions were correct (167 of 241, 69.3%) indicating that a disguise/simulation process was detected, but misinterpreted as being by another writer. These results show the usefulness of FHEs offering a first stage simulation/disguise process opinion without going on to form an opinion on authorship, as the support for the proposition that a signature is something other than genuine may be, in itself, of strong evidential value.