  In this article, the general solution of the tachyonic Klein-Gordon equation
is obtained as a Fourier integral performed on a suitable path in the complex
\omega-plane. In particular, it is proved that under given boundary conditions
this solution does not contain any superluminal components. On the basis of
this result, we infer that all possible spacelike wave equations describe the
dynamics of subluminal particles endowed with imaginary mass. This result is
validated for the Chodos equation, used to describe the hypothetical
superluminal behaviour of neutrino. In this specific framework it is proved
that the wave packet propagates in spacetime with subluminal group velocities
and that for enough small energies it behaves as a localized wave.
