  The formalism of Operational Dynamical Modeling [Phys. Rev. Lett. {\bf 109},
190403 (2012)] is employed to analyze dynamics of spin half relativistic
particles. We arrive at the Dirac equation from specially constructed
relativistic Ehrenfest theorems by assuming that the coordinates and momenta do
not commute. Forbidding creation of antiparticles and requiring the
commutativity of the coordinates and momenta lead to classical Spohn's equation
[Ann. Phys. {\bf 282}, 420 (2000)]. Moreover, Spohn's equation turns out to be
the classical Koopman-von Neumann theory underlying the Dirac equation.
