  If the observation by OPERA of apparently superluminal neutrinos is correct,
the Lagrangian for second-generation leptons must break Lorentz invariance. We
calculate the effects of an energy-independent change in the neutrino speed on
another observable, the charged pion decay rate. The rate decreases by an
factor [1 - 3/(1 - (m_mu)^2 / (m_pi) ^ 2) (< v_(nu) > - 1)], where < v_(nu) >
is the (directionally averaged) neutrino speed in the pion's rest frame. This
provides a completely independent experimental observable that is sensitive to
the same forms of Lorentz violation as a neutrino time of flight measurement.
