Measurement of Michel Parameters and $\tau$ Neutrino Helicity in $Z^{0} \to \tau^{+}\tau^{-}$

Data sets comprising 24 pb**-1 collected with the ALEPH detector a LEP in 1990 to 1992 were used to measure the Michel Parameters and the mean tau polarisation. The assumption of v and a type couplings in the production of the tau pairs allowed the correlation of the heli- cities of the tau+ and tau- to be used to derive the information on the neutral and charged weak current. The Michel Parameters rho, ksi and for the first time delta are measu- red for the leptonic tau decays. In the hadronic tau decays into pion and rho the ksi parameter which equals the average tau neutrino heli-city is determined. All measurements show agreement with the Standard Model expectation at the current level of precision.