Localization and noncausal behaviour of relativistic quantum particles

Hegerfeldt proved that the localization of a relativistic quantum particle in a finite-space region V, at a given time t0, implies that the probability of finding the particle, at a later time t, at a distance abs(a) > c(t-t0), is nonzero. It is shown that this mechanism cannot be used in the transmission of signals and therefore there is no conflict with relativistic causality