  We generalize our previous work on gravitational lensing by a Kerr black hole
in the strong deflection limit, removing the restriction to observers on the
equatorial plane. Starting from the Schwarzschild solution and adding
corrections up to the second order in the black hole spin, we perform a
complete analytical study of the lens equation for relativistic images created
by photons passing very close to a Kerr black hole. We find out that, to the
lowest order, all observables (including shape and shift of the black hole
shadow, caustic drift and size, images position and magnification) depend on
the projection of the spin on a plane orthogonal to the line of sight. In order
to break the degeneracy between the black hole spin and its inclination
relative to the observer, it is necessary to push the expansion to higher
orders. In terms of future VLBI observations, this implies that very accurate
measures are needed to determine these two parameters separately.
