  We find very good agreement between our theoretically evaluated lifetimes of
the $5d \ ^2D_{3/2}$ and $5d \ ^2D_{5/2}$ states of Cs with the experimental
values reported in [Phys. Rev. A {\bf 57}, 4204 (1998)], which were earlier
evinced to be disagreeing with an earlier rigorous theoretical study [Phys.
Rev. A {\bf 69}, 040501(R) (2004)] and with another precise measurement [Opt.
Lett. {\bf 21}, 74 (1996)]. In this work, we have carried out calculations of
the radiative transition matrix elements using many variants of relativistic
many-body methods, mainly in the coupled-cluster theory framework, and analyze
propagation of the electron correlation effects to elucidate their roles for
accurate evaluations of the matrix elements. We also demonstrate contributions
explicitly from the Dirac-Coulomb interactions, frequency independent Breit
interaction and lower order quantum electrodynamics (QED) effects.
Uncertainties to these matrix elements due to different possible sources of
errors are estimated. By combining our calculated radiative matrix elements
with the experimental values of the transition wavelengths, we obtain the
transition probabilities due to both the allowed and lower order forbidden
channels. Adding these quantities together, the lifetimes of the above two
states are determined precisely and plausible reasons for the reported
inconsistencies between the earlier theoretical calculations and the
experimental results have been pointed out.
