Direct CP Violation in the $B^{0}_{s}$ meson

The $B^{0}_{s} \rightarrow K^{-} \pi^{+}$ decay mode, recently observed at CDF, is a good candidate for observing direct CP violation in the $B^{0}_{s}$, and offers a unique opportunity for testing the reliability of Standard Model predictions, especially in the light of the large asymmetry observed in the $B^{0} \rightarrow K^{+} \pi^{-}$ mode. We describe the latest update of this measurement, using an improved analysis method, and a data set of about 5 fb$^{-1}$ of $p\overline{p}$ collisions collected by the updgraded CDF detector.