  We show the uniqueness of particle paths of a velocity field, which solves
the compressible isentropic Navier-Stokes equations in the half-space
$\mathbb{R}_+^3$ with the Navier boundary condition. In particular, by means of
energy estimates and the assumption of small energy we prove that the velocity
field satisfies the necessary regularity needed to prove the uniqueness of
particle paths.
