  Employing colliding-pulse injection has been shown to enable high-quality
electron beams to be generated from laser-plasma accelerators. Here by
leveraging test particle simulations, Hamiltonian analysis, and
multidimensional particle-in-cell (PIC) simulations, we lay the theoretical
framework of spin-polarized electron beam generation in the colliding-pulse
injection scheme. Furthermore, we show that this scheme enables the production
of quasi-monoenergetic electron beams in excess of 80\% polarization and tens
pC charge with commercial 10-TW-class laser systems.
