  We investigate $L^1\to L^\infty$ dispersive estimates for the three
dimensional Dirac equation with a potential. We also classify the structure of
obstructions at the thresholds of the essential spectrum as being composed of a
two dimensional space of resonances and finitely many eigenfunctions. We show
that, as in the case of the Schr\"odinger evolution, the presence of a
threshold obstruction generically leads to a loss of the natural $t^{-\frac32}$
decay rate. In this case we show that the solution operator is composed of a
finite rank operator that decays at the rate $t^{-\frac12}$ plus a term that
decays at the rate $t^{-\frac32}$.
