1. In a signature verification system including a stylus capable of sensing pressure in two orthogonal (x,y) directions and generating signals proportional thereto, a method of normalizing the signals generated by the stylus such that the result is insensitive to the rotational position of the stylus with respect to the writer's grip comprising the steps of: generating first and second distinct trains of output signals each of which is proportional to the forces exerted on the stylus in one of two orthogonal (x,y) directions; sampling the first and second trains of output signals at discrete intervals during a signature; computing an angle representative of the average direction of the signature; normalizing each sample by said computed angle; and comparing the normalized samples with a reference signature to verify the identity of the writer.