  The Bs meson is an interesting particle to study because a sizable mixing
induced CP violation in the Bs-Bsbar system would be an indication for physics
beyond the Standard Model. In this paper we present a measurement of the
lifetime difference DeltaGamma between the Bs mass eigenstates and the CP
violating phase in the decay Bs -> J/psi phi. In 1.7 fb^-1 of data collected
with the CDF II detector at the Tevatron ppbar collider we measure DeltaGamma =
0.076 +0.059-0.063 (stat.) +- 0.006 (syst.) ps^-1, well consistent with the
Standard Model prediction, and a mean Bs lifetime of ctau_s = 456 +-13 (stat.)
+- 7 (syst.) m^-6. We find no evidence for CP violation.
