Abstract: A method of associating handwriting with an individual, or authenticating a document or transaction based on handwriting of one or more individuals is provided, the method including (a) collecting by operation of a handwriting instrument, biometric data from a plurality of instances of handwriting of at least one individual, such biometric data including grip pressure and optionally including axial pressure, so as to create a set of handwriting biometric data elements; (b) modeling the handwriting biometric data elements to create, or facilitate the creation of, a functional characteristic model for the handwriting of each of the at least one individual; and (c) associating each of one or more target instances of handwriting with an individual associated with such handwriting based on the functional characteristic model, and optionally based on such association(s) authenticating a document or transaction.