  We investigate electron vortex beams elastically scattered on chiral
crystals. After deriving a general expression for the scattering amplitude of a
vortex electron, we study its diffraction on point scatterers arranged on a
helix. We derive a relation between the handedness of the helix and the
topological charge of the electron vortex on one hand, and the symmetry of the
Higher Order Laue Zones in the diffraction pattern on the other for
kinematically and dynamically scattered electrons. We then extend this to atoms
arranged on a helix as found in crystals which belong to chiral space groups
and propose a new method to determine the handedness of such crystals by
looking at the symmetry of the diffraction pattern. Contrary to alternative
methods, our technique does not require multiple scattering which makes it
possible to also investigate extremely thin samples in which multiple
scattering is suppressed. In order to verify the model, elastic scattering
simulations are performed and an experimental demonstration on
Mn$_2$Sb$_2$O$_7$ is given where we find the sample to belong to the right
handed variant of its enantiomorphic pair. This demonstrates the usefulness of
electron vortex beams to reveal the chirality of crystals in a transmission
electron microscope and provides the required theoretical basis for further
developments in this field.
