The accuracy and validity of the Sheffield Features of Gait Tool

Gait is now widely used in the UK as a contributor to identification, and increasing interest is being shown in its use in both Europe and the US. One of the long standing criticisms of the use of gait as evidence has been the lack of a validated standard methodology. With the publication of the 'Code of practice for forensic gait analysis', and the adoption of the code as part of the 'Codes of Practice and Conduct for forensic science providers and practitioners in the Criminal Justice System' by the Forensic Science Regulator, forensic gait analysts are now required to provide evidence of the testing of the methods used. The Sheffield Features of Gait Tool is specifically designed to assist observational gait analysis in the forensic context, and was developed by forensic gait analysis practitioners based on their casework and trial experience. Birch et al 2019 reported the findings of a study undertaken to assess the repeatability and reproducibility of the tool. This paper reports the findings of a study undertaken to assess the accuracy with which analysts identified features of gait when using the tool. Fourteen participants, with experience in observational gait analysis, viewed footage of computer generated avatars walking, and completed the features of gait tool on multiple occasions. The results showed a mean accuracy score of 134.92 out of a possible 180 (74.96%), a standard deviation of 9.49 (5.27%) and a coefficient of variation of 7.03%, demonstrating a good degree of consistency between the scores (Cronbach's alpha <0.90; ANOVA p-value <0.05). The findings of this study, coupled with those of the Birch et al 2019 study which showed there to be good levels of both repeatability and reproducibility of observations of features of gait made by the participants, suggest that the Sheffield Features of Gait Tool is a valid and fit for purpose method of observing and recording features of gait in the forensic context. The use of the tool provides the basis of a standardised methodology for observational gait analysis in the forensic context.