  The Kerr spacetime is symmetric with respect to a well-defined equatorial
plane. When testing the equatorial reflection symmetry of an isolated black
hole, one is at the same time testing the Kerr hypothesis in General
Relativity. In this work, we investigate the possible observational features
when a Keplerian disk is surrounding a rotating black hole without reflection
symmetry. When such symmetry is broken, generically, the photon trajectories
around the black hole and the Keplerian orbits on the accretion disk are
distorted vertically away from the equatorial plane by an amount that depends
on their distance to the black hole. In the reflection asymmetric spacetime we
are considering, these two kinds of orbits are distorted in opposite
directions. Interestingly, while the size and shape of black hole shadows
closely resemble those of Kerr black holes, distinct observational
characteristics can emerge in the disk image and emission line profiles. When
observing the disk edge-on, a pronounced concave shape may appear along its
innermost edge on the incoming side. Furthermore, distinctive horn-like
features might be observed on the spectral line profile at the blue-shifted
side. These special features can serve as compelling indicators of the
reflection asymmetry present in rotating black holes.
