  This study reconsiders the decay of an ordinary particle in bradyons,
tachyons and luxons in the field of the relativistic quantum mechanics. Lemke
already investigated this from the perspective of covariant kinematics. Since
the decay involves both spacelike and timelike particles, the study uses the
Majorana equation for particles with an arbitrary spin. The equation describes
the tachyonic and bradyonic realms of massive particles, and approaches the
problem of how spacelike particles might develop. This method confirms the
kinematic constraints that Lemke theory provided and proves that some possible
decays are more favourable than others are.
