In this paper a study of some structural features of hand-written letter ?a? is presented. The features under consideration are structural, style and formation features document examiner?s use when studying a questioned document to determine its authorship or authenticity. Feature extraction algorithms for the feature set were developed to perform the extraction procedure automatically. The estimate of feature consistency is introduced and measured for each extracted feature. The extracted feature set is analyzed for linear independency and ability to be used for separation of author classes (i.e. authorship decision). The results on a set of 18 authors with approximately 40 letter ?a?s per author indicates a high level of consistency and discrimination ability for most of the features analysed.