  We present a new method to measure the transverse spin correlation in the
$H\to\tau^+\tau^-$ decay. The method has been devised to be insensitive to the
beamstrahlung which affects the definition of the beam energy at a linear
collider. In the case of two $\tau\to\pi^\nu$ decays, using the anticipated
detector performance of the TESLA project, we get a promising estimation of the
error expected on the measurement of a CP violating phase.
