  We explore constraints imposed by shear-driven instabilities on the
acceleration of energetic particles in relativistic shearing flows. We show
that shearing layers in large-scale AGN jets are likely to encompass a sizeable
fraction ($\geq 0.1$) of the jet radius, requiring seed injection of GeV
electrons for efficient acceleration. While the diffusion process may depend on
pre-developed turbulence if injection occurs at higher energies, electron
acceleration to PeV and proton acceleration to EeV energies appears possible
within the constraints imposed by jet stability.
