  We examine how initial coherences in open chiral systems affect
distinguishability of pure versus mixed states and purity decay. Interaction
between a system and an environment is modeled by a continuous position
measurement and a two-level approximation is taken for the system. The
resultant analytical solution is explored for various parameters, with emphasis
on the interplay of initial coherences of the system and dephasing rate in
determining the purity decay and differences in the time evolution of pure vs.
mixed initial states. %the distinguishability and the decoherence process.
Implications of the results on several fundamental problems are noted.
