Michael (Professor of Computer Vision, University of Kent, School of Engineering and Digital Arts, UK) Fairhurst 
Age Factors in Biometric Processing [PDF ebook] 

As biometrics-based identification and identity authentication become increasingly widespread in their deployment, it becomes correspondingly important to consider more carefully issues relating to reliability, usability and inclusion. One factor which is particularly important in this context is that of the relationship between the nature of the measurements extracted from a particular biometric modality and the age of the sample donor, and the effect which age has on physiological and behavioural characteristics invoked in a biometric transaction.