A comparative review of error rates in forensic handwriting examination

A comparison of error rates between studies in forensic handwriting examination has been made in response to the lack of knowledge on error in this field. Fifteen indicators have been used to describe and compare error rates between studies. The results of each study have been processed to determine these indicators. Parameters related to the participants, conclusion scale, amount of time allocated to the task, and the task itself are also reported. The error rate indicators are provided for each study, and then combined across studies using values of mean and standard deviation. Experts were found to perform better than laypeople. For handwritten texts, absolute error rate for experts ranges from 0.32% to 5.85% (with a mean of 2.84 ± 2.33%), and for laypeople from 11.43% to 28.72% (with a mean of 21.40 ± 8.94%). For signatures, absolute error rate for experts ranges from 0% to 4.86% (with a mean of 2.50 ± 1.55%), and for laypeople from 10.68% to 28% (with a mean of 19.55 ± 7.05%). Overall, experts have an absolute error rate of 2.63 ± 1.73% (against 20.16 ± 7.20% for laypeople). Experts are also more likely to give inconclusive answers than laypeople. Overall, the rate of absolute inconclusive answers for experts is 21.96 ± 23.15% (against 8.13 ± 7.96% for laypeople). The comparative review of error rates presented in the present article contributes to validating the discipline by showing how research has been devoted to meeting the criteria of testing to be considered scientific.