  This work introduces a novel formalism to investigate the role of the spin of
astrophysical black holes in determining the behaviour of matter falling onto
such accretors. Equations describing the general relativistic hydrodynamic
accretion flow in the Kerr metric are formulated, and stationary solutions for
such flow equations are provided. The accreting matter may become
multi-transonic, allowing a stationary shock to form for certain initial
boundary conditions. Such a shock determines the disc geometry and can drive
strong outflows. The properties of matter extremely close to the event horizon
are studied as a function of the Kerr parameter, leading to the possibility of
detecting a new spectral signature of black hole spin.
